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EuropeanJournal ofPopulation 11: 63-84, 1995. © 1995 KluwerAcademicPublishers. Printedin the Netherlands. 63 Infant Health and Mortality Indicators Their Accuracy for Monitoring the Socio-Economic Development in the Europe of 1994 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN Insfitut de Ddmographie, UniversitdCatholique de Louvain, 1 PlaceMontesquieu, bte 17, B-1348 Louvain-la-Neuve, Belgium Received 28 April 1994; accepted in final form 15 December 1994 Masuy-Stroobant, G. and Gourbin, C., 1995. Infant health and mortality indicators. Their accuracy for monitoring the socio-economic development in the Europe of 1994. European Journal of Popula- tion/Revue Europrenne de Drmographie, 11: 63-84. Abstract. The ability of infant mortality and health indicators to monitor health conditions in early infancy, and their broader use as indicators of the general level of socio-economic development are discussed from three points of view. These are: (i) the increasing impact of differences in legal definitions of live and stillbirths on the comparability of the infant mortality figures produced by vital statistics; (ii) the validity of mortality measures to monitor health; (iii) the comparability of social inequalities in infant health and mortality over time and across countries. Masuy-Stroobant, G. and Gourbin, C., 1995. Indicateurs de sant6 et de mortalit6 infantile. Leur pertinence comme indicateur du drveloppement 6conomique et social de l'Europe de 1994. Euro- pean Journal of Population/Revue Europrenne de Drmographie, 11: 63-84. Rrsum~. La validit6 de la mesure de la mortalit6 infantile comme indicateur de drveloppement 6conomique et social est remise en question dans le contexte de la situation actuelle en Europe. Trois axes de l"rflexionsont envisagrs: l'impact croissant de diffrrences dans les crit~res 16gaux de drfinition des naissances vir~antes et des naissances d'enfants mort-nrs sur les niveaux de mortalit6 infantile foumis par les statistiques d'rtat civil; la pertinence de mesures de mortalit6 comme indicateurs de sant6 infantile; la comparabilit6 dans le temps et dans l'espace des inrgalitrs sociales de sant6 et mortalit6 infantile. 1. Introduction The infant mortality rate defined as the risk of a livebom child dying before its first birthday (usually expressed by the number of deaths of infants in a year per thousand live births in that year), is known to be one of the most sensitive and commonly used indicators of the social and economic development of a population (Woodbury, 1925; Stockwell, 1962; Brenner 1973; Adamchak, 1979; Basch, 1990). Socially visible and even statistically measurable, the association between deprivation and poor survival in infancy originated probably in the process of

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Page 1: Infant health and mortality indicators

European Journal of Population 11: 63-84, 1995. © 1995 KluwerAcademic Publishers. Printed in the Netherlands.

63

Infant Health and Mortality Indicators Their Accuracy for Monitoring the Socio-Economic Development in the Europe o f 1994

G O D E L I E V E M A S U Y - S T R O O B A N T AND CATHERINE G O U R B I N Insfitut de Ddmographie, Universitd Catholique de Louvain, 1 Place Montesquieu, bte 17, B-1348 Louvain-la-Neuve, Belgium

Received 28 April 1994; accepted in final form 15 December 1994

Masuy-Stroobant, G. and Gourbin, C., 1995. Infant health and mortality indicators. Their accuracy for monitoring the socio-economic development in the Europe of 1994. European Journal of Popula- tion/Revue Europrenne de Drmographie, 11: 63-84.

Abstract. The ability of infant mortality and health indicators to monitor health conditions in early infancy, and their broader use as indicators of the general level of socio-economic development are discussed from three points of view. These are: (i) the increasing impact of differences in legal definitions of live and stillbirths on the comparability of the infant mortality figures produced by vital statistics; (ii) the validity of mortality measures to monitor health; (iii) the comparability of social inequalities in infant health and mortality over time and across countries.

Masuy-Stroobant, G. and Gourbin, C., 1995. Indicateurs de sant6 et de mortalit6 infantile. Leur pertinence comme indicateur du drveloppement 6conomique et social de l'Europe de 1994. Euro- pean Journal of Population/Revue Europrenne de Drmographie, 11: 63-84.

Rrsum~. La validit6 de la mesure de la mortalit6 infantile comme indicateur de drveloppement 6conomique et social est remise en question dans le contexte de la situation actuelle en Europe. Trois axes de l"rflexion sont envisagrs: l'impact croissant de diffrrences dans les crit~res 16gaux de drfinition des naissances vir~antes et des naissances d'enfants mort-nrs sur les niveaux de mortalit6 infantile foumis par les statistiques d'rtat civil; la pertinence de mesures de mortalit6 comme indicateurs de sant6 infantile; la comparabilit6 dans le temps et dans l'espace des inrgalitrs sociales de sant6 et mortalit6 infantile.

1. Introduction

The infant mortality rate defined as the risk of a l ivebom child dying before its first

birthday (usually expressed by the number of deaths of infants in a year per thousand

live births in that year), is known to be one of the most sensitive and commonly

used indicators o f the social and economic development of a population (Woodbury,

1925; Stockwell, 1962; Brenner 1973; Adamchak, 1979; Basch, 1990). Socially visible and even statistically measurable, the association between

deprivation and poor survival in infancy originated probably in the process of

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64 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

XIXth Century industrialization. It was documented with survey data as early as 1824 (Villerm6, 1830, quoted by Lesa~ge-Dugied, 1972). The association between socio-economic factors and infant mortality was further reinforced at a more aggre- gate level when improvements in overall infant mortality levels over time ran paral- lel with general social and economic development in most industrialized countries during the XXth Century. Infant mortality began to decline in Western European countries at the onset of this century and its use as an indicator of a certain level of 'development' was already documented in 1910: 'Infant mortality is the most sensitive index we possess of social welfare and sanitary administration' (Newsholme, 1910 quoted by Yankauer, 1990). Furthermore, since the Second World War, corroboration of the strong inverse relationship between economic development and mortality rates has been found repeatedly among countries and areas within countries at any given time. Intemational comparisons between highly developed Western European countries and the Third World in this respect need no further comment, but the same association is found when Western and East- ern European countries are considered and even within Western Europe (Fender and Br6art, 1981). Regional development is also invoked when regional infant mortality differences are observed within countries. At this level, links between individual-level social inequalities and regional (aggregate-level) differences are partly explained by unequal spatial concentrations of the deprived and of popula- tions of lower social class (United Nations, 1953; Masuy-Stroobant, 1983).

2. Development

Although the relationship is almost universally observed and duly documented, its causal nature is still difficult to assess. 'The reasons are not well understood as many changes in development could be contributory...' (DaVanzo, 1985). One of the many unsolved problems is linked to the meaning of the concept of 'development' itself and the way it is measured when analyzed in terms of infant mortality. The definition and measurement of development have undergone changes over the years and moved from a basically economic view after the second World War towards a more holistic conception in the mid-sixties (Bauer, 1966; Galtung and Wirak, 1979; Carley, 1981). When the former definition was used, development was measured c~xclusively by economic growth indicators (Gross National Product, per capita income, etc.). The by-product of economic growth was supposed to bring about increasing expenditure on sanitation and other public health measures, education, housing, etc.; all important determinants of mortality levels (United Nations, 1953). But at the individual (Caldwell, 1979; Bicego and Boerma, 1993; Hobcraft, 1993) and at the aggregate level (Loriaux and Remy, 1980) other indicators proved to be more efficient in predicting infant mortality risks: among others, education seems to play an important role. Education is part of what Morris and Heady considered to be 'capital assets' giving access to the improved satisfaction of basic needs, including occupation, income, housing, and increasing the capacity of the

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INFANT HEALTH AND MORTALITY INDICATORS 65

population (especially the mothers) to cope with health problems in general (Morris and Heady, 1955). Furthermore, general access to education implies the possibility of reducing inequalities, and of increasing rational use of available resources, all elements contributing to more social as well as global conceptions of development. The one-sided economic definition of development widened during the seventies: 'There is a growing awareness that 'development' cannot be measured in economic terms only but that the ultimate goal of development is the improvement of quality of life and the best feasible satisfaction of human needs and aspirations. (...) health is an integral and essential component of the general development strategy' (World Health Organization, 1974). As integral part of the social components of this broader concept of development, health indicators are more often embedded in its measurement, which means that infant mortality (among others) is included in the measure of development (Agbonifo, 1983). Considered thus to be part of the social and economic development process, the causality debate becomes somewhat meaningless, but infant mortality is still considered to be a valid indicator of development.

3. Infant mortality

The progress achieved in reducing infant mortality since the nineteenth century has been impressive. Moving from a very high level through the whole XIXth Century, with about one out of five or six newborns dying within the first year of life, infant mortality figures today are concentrated around one percent in several European countries. But within this general picture of an improving infant survival rate, one observes some persistent aspects of inequality: the international and regional differences at the aggregate level, often thought to be linked to unequal socio-economic development, and social inequalities at the individual level.

The XXth Century infant mortality history in Westem Europe moved along a typical four-stage pattern, which may be associated with the gradual medicaliza- tion of motherhood. The two World War periods exerted a positive effect on the organization of maternal and child health care: the crisis created by the First World War is linked to the effective start of maternal and child health systems in many countries with the first concerted attempt to organize local child health clinics and in some countries, to provide nutritional supplements by means of milk depots (Masuy-Stroobant, 1983). Acceleration of the hospital delivery process became significant in the years following the Second World War with the spread of social security systems in Europe. Further to those two major events, a sustained and permanent decline of the postneonatal mortality rate started in the early twenties, while improvements in maternal mortality and first signs of a drop in early neonatal mortality were observed in the early fifties. Stillbirth rates began to decline in the interwar period when antenatal clinics were organized on a more systematic basis. More recently, the provision of neonatal intensive care units during the eighties led to a further drop in early neonatal mortality.

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66 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

Together with this secular decrease of the overall infant mortality rate, the age at death and distribution of causes of death changed also. For centuries, infant mortality remained at very high levels, although declines were observed in some countries in the eighteenth century. It was mainly posmeonatal and of infectious origin, while at present, it is increasingly located in the very early days or even hours of life. Hence the importance given today to early neonatal mortality (deaths occurring during the first week) which accounts for about 50% of total infant mortality all over Europe. Consequently, conditions related to immaturity and, to a less extent, congenital anomalies, are now the leading causes of death in early infancy. Due to similar medical causes, late foetal deaths (or stillbirths) were considered to be at least partly avoidable or preventable. This evolution led to a redefinition of the concept of infant mortality itself, grouping stillbirths and early neonatal mortality together into one global indicator, the perinatal mortality rate (Peller, 1948).

Further to these basic changes in infant mortality and related indicators, their adequacy as monitors of health conditions in early infancy and also their broader use as indicators of the general socio-economic development level can be discussed from (at least) three points of view:

1. In considering perinatal mortality as a more specific indicator of what is happening in very early infancy, one has to consider the accuracy and hence the validity and comparability over time and accross countries of the livebirth and stillbirth definitions embedded in this indicator (Section 4).

2. Mortality measures are often used to monitor the health level of the age group. Whether improved survival of very low birthweight babies implies also a decrease in the risks of associated handicaps is still to be evaluated. In other words are infant or perinatal mortality rates still valid indicators of the infant or perinatal health (Section 5)?

3. The general feeling that mortality linked to environmental and social factors in early infancy has fallen with the dramatic decrease in mortality from infectious diseases is contradicted by persistent social differences observed even in countries with the lowest infant mortalities. Whatever the lifetime considered, social inequalities in late foetal, early neonatal, late neonatal and postneonatal mortality are still significant everywhere in Europe. The question here is to know whether these inequalities are widening or decreasing over time and how they could be compared across countries (Section 6).

4. Are live and stillbirths comparable all over Europe?

Infant mortality figures are usually produced by vital registration statistics. They are still a by-product of legal requirements and therefore depend closely on the legal definitions of the relevant vital events: stillbirths, livebirths and deaths. Beside legal rules and obligations, the impressive performances of neonatal intensive care techniques during the eighties led to a redefinition of the de facto viability

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INFANT HEALTH AND MORTALITY INDICATORS 67

criteria, which vary within and across countries according to the availability of adequate neonatal care (Fenton et al., 1990; Gourbin and Masuy-Stroobant, 1993). Obstetric practice changed accordingly, and the decision to proceed to delivery of immature foetuses at risk of dying in utero exerts a significant impact on the overall incidence of such infants. This may lead to a shift towards registration of a live birth instead of a stillbirth (or of no registration at all, if the foetal death occurred below the minimum required gestational age for being considered as a stillbirth). Legal criteria defining the requirement to register births (live and still) may in some countries no longer match medical reality. Consequently it has been suggested (Working Group on the Very Low Birthweight Infant 1990) that perinatal mortality considered as a global indicator is no longer able to reflect adequately improvements occuring in perinatal care as it relies more and more on the availability of highly specialized care and mixes prenatal and neonatal factors as well as registration rules and practices. Accordingly, the impact of differences in legal definitions in the registration practices and data processing methods is presumably rising, especially when early neonatal and perinatal mortality indicators are considered.

4.1. DE FACTO AND DE JURE DEFINITIONS

The decision to declare is a necessary condition for registration. This decision relies mainly on the birth attendant, his knowledge of the definitions and, for very preterm births, on his expectancies of their chances of survival (Keirse, 1984; Herthoghe et al., 1987). Furthermore, the legal aspects (rights and obligations) linked to the registration of birth may in some cases induce the birth attendant to depart from the rules. The comparative social advantages (birth and child allowances) attached to the declaration of a live birth versus a stillbirth constitutes for some borderline cases another possible cause of distortion (Keirse, 1987). Cultural factors, like religion, were sometimes argued to explain Shifts in declaration from stillbirth to a live birth (to be baptised) (Lindsay, 1985; Moreau and Rousseau, 1986). Finally, the political importance given today to the infant mortality figures could have been responsible for selective declaration of the healthiest infants, hence artificially lowering overall infant mortality and more specifically early neonatal mortality (Gourbin and Masuy-Stroobant, 1993).

Beside those legal, social or cultural factors, the 24 hours survival criterion is presumably far more common in every-day practice than is supposed by the existing legal or administrative rules. Obviously, vital registrationof very preterm livebom children who die shortly after birth could be influenced by the access to specialized neonatal care, legal and social consequences linked to vital registration, etc. (Fenton et al., 1990; Gourbin, 1991). Conceming the accuracy and comparability of neonatal or global perinatal mortality figures, the most worrying fact is that, when those very preterm infants are not registered as live births, they usually also fail to meet the minimum criteria for stillbirth, and are thus not registered at all (Dumoulin an0~

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68 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

Countries ranked by Infant mortal i ty rate

<24 hours

~,1 (1986) U.S.S.R.

23.5 (1989) YUGOSLAVIA l 16.0 (1989} ~ L ~ D l

14.8 (1990) HUNGARY l 13.1 (1988) PORTUGAL l I1.3(1989)~ECHOSL. l

II .0(1988) GREECE l 9.7 (1987) BELGIUM 1

9.2 (1988) ITALY 1 8.9 (1988) N. IRELAND

8,7 (1989) SCOTLAND l 8.6 (1989) LUXEMBURG

8,5 (1989) ~GL-WALES l 8,2 (1976-80) ICELAND l

8,0 (1988) SPAIN l 7.9 (1987) (REP.) IRELAND

7.9 (1989) NORWAY

7.8 (1990) AUSTRIA l 7.8 (1987) FRANCE

7.4 (1990) DENMARK l 7,4 (1989) G.F.R.

7.3 (1989) S ~ E R L ~ D

6,8 (1988) NETHERLANDS l

6,4(1989) SWEDEN 1 6,1 (1988) FINLAND l

I-6 days 7-27 days 28-364 days

l l l l l ~ ,

Fig. 1.

~ _ _ - - < ,:::( 8

~ _ _ . ..-:: 2

- . { t

- - :: I

" " 2 2

] [ Z l m l l m :

I "T I I

20% 0%

Source : Vital Regt~tration

40% 60% 80% 100%

(1) 1985.87 (3) 1987-89 (5) 1985-90 (7)1988-89 (2) 1985-88 (4) 1985,86 (6) 1989-90 (8)1976-80

Infant death; distribution by age. Europe 1985-1989.

Gourbin, 1991). Consequently, deaths very early in infancy need to be considered separately from those occuring later. It is suggested (Masuy-Stroobant, 1995) to take as a crucial divide, survival to 24 hours of age, deaths occurring during the first day of life being the most subject to underreporting. Comparable early neonatal

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INFANT HEALTH AND MORTALITY INDICATORS 69

14

12

10

8

6

4

QI-6days

I ~ I I I I I I I [ I I I I I I I I I I I I

1965 1970 1975 1980 1985

Early neonatal mortality. Czechoslovakia 1950-1985.

2

0 I I B I I I I I I I I

1950 1955 1960

Source : Vital Registration

Fig. 2.

figures could then be obtained in reference to the remaining days of the first week of life (denominator of the risks should then be survivors at 24 hours).

When considering the age at death structure for total infant (liveborn) deaths (Fig. 1), one observes a general pattern towards a near 50% concentration of total infant deaths within the first week, of which 50% (25% of total deaths) occur during the first 24 hours.

The evolution of the first-day mortality is an excellent indicator of (legal) birth definition and registration problems.

Czechoslovakia is one of the many examples of the impact changes in legal definitions and data processing methods can have on the published evolution of first- day mortality and hence on the general level of infant mortality. As a consequence of the adoption (1965) of the WHO definition of a live birth, one observes a sudden upward trend of the first day infant mortality risk (Fig. 2). Furthermore, first day mortality was calculated by difference in calendar days up till 1985 leading to an important underestimation of the real first 24 hours mortality.

The U.S.S.R. registration of early neonatal deaths is obviously underestimated (underregistered), survival during a whole week being required for live births who are born before 28 weeks of gestation, or weighing less than 1,000 g or less than 35 cms crown-rump length (Fig. 1).

However, the calculation of comparable and accurate measures of the first-day mortality and of the survivors at 24 hours of life, depends on the availability of the necessary basic information. In this case, exact date and time (hours, minutes) at birth and death is requested for deaths occuring within the first 24 hours. Life duration calculated by difference of calendar days mostly underestimates first-day mortality, with a chain-effect on the accuracy of the risks at the next age intervals. In Czechoslovakia, for instance, where both figures are published for 1989, 397

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70 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

TABLE 1. Stillbirths, live births and infant deaths with less than 28 completed weeks of gestation. Selected European countries. Absolute numbers and (percentages)

Country Stillbirth Live birth Deaths 0-6 days 0-27 days < 1 year

Austria - 1990 22 (6.8) 253 (0.3) 96 (32.3) 128 (31.9) 136 (19.2) Belgium - 1988 49 (7.2) 185 (0.2) 88 (37.3) 100 (16.1) 111 (10.3) Hungary -1990 - 564 (0.4) 376 (34.4) - - Italy - 1985 212 (5.5) 1237 (0.2) 940 (24.4) 1057 (22.8) 1098 (18.8) Portugal a - 1990 198 (20.8) 259 (0.2) - -

Source: Vital Registration. a The registration criterion for stillbirths is fixed at 22 weeks of gestation.

deaths occurred during the first day (calculated by difference in calendar days) whereas 541 liveborns died within the first 24 hours of life.

4.2. INTERNATIONAL COMPARISONS

Another important consequence of the problems of definition is the lack of interna- tional comparability of perinatal and infant mortality figures. Hence, the collapsing of stillbirths and early neonatal deaths into a single global indicator may further bias comparisons over time and space in different ways.

When late foetal deaths, or stillbirths, are considered for vital registration, one observes a general tendency to adopt similar definitions across Europe. In 21 countries (Gourbin and Masuy-Stroobant, 1993) only foetal deaths occurring at a minimum gestational age of 28 weeks, or the corresponding birthweight (1,000 g) or body length (35 cm) are eligible for vital registration and included in national statistics. On the other hand, vital registration of very preterm liveborn infants with gestation durations as low as 26 to 24 weeks, is no longer unusual even though their mortality risks still remain at very high levels (Table 1).

Perinatal mortality figures thus often mix adverse pregnancy outcomes with different gestation durations. The notion of viability of the newborn, closely linked to a minimum gestation duration, is expanding for live births, but not for stillbirths, due to the constraints of more rigid legal definition. Since (published) vital reg- istration statistics usually do not standardize their perinatal mortality figures for birthweight or gestation duration, the relevant events (stillbirths and early neonatal deaths) therefore belong thus to increasingly divergent categories of viability.

Accordingly we recommend that stillbirth rates should be calculated separately from early neonatal mortality. Mortality within the first week should be disaggre- gated by distinguishing deaths occuring during the first 24 hours from the remainder. It is noteworthy that the first-day mortality is still not calculated the correct way in every country.

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INFANT HEALTH AND MORTALITY INDICATORS 71

5. Does mortality measure health?

For operational reasons (availability of the data through vital registration) and reliability of its measurement, health indicators are often expressed in terms of mortality:

Les indicateurs de mortalit6 ne peuvent rendre compte du poids des probl~mes de sant6 (...) que pour des phrnomrnes pathologiques se traduisant par un drc~s prrmatur6 (Goldberg, 1979).

The most fundamental criticism one may address to this traditional practice is that infant health is thereby measured by an indicator of extreme ill-health. Furthermore, mortality reflects only the negative and strictly biological dimension of health. If there is sufficient evidence that the secular trend of decrease in infant mortality does adequately reflect parallel improvements in the health situation in early infancy (Blaxter, 1981), this association is more controversial today due to the increasing performances of neonatal intensive care techniques. However, improved survival of even smaller babies does not per se imply that they are free from impairments and disabilities, or more important, brain damage often linked to extreme immaturity.

5.1. BIRTHWEIGHT AND GESTATIONAL AGE

With the very low infant mortality levels encountered in Europe and the impressive efficacy of neonatal intensive care techniques leading to the survival of babies with even lower birthweight and of even shorter gestation, concern for infant health and its measurement is growing. Hence the search for adequate definitions and indicators. The concept of 'Very Low Birthweight' (children weighing less than 1,500 g at birth) tends to replace the previous concept of 'Low Birthweight' (less than 2,500 g) as a criterion for defining high risk groups in the international literature. This tendency reveals the progress achieved in the survival of children weighing 1,500 g to 2,500 g at birth and also a shift in the de facto viability criteria, the latter increasing most probably in keeping with the registration of very low birthweight infants.

Birthweight or gestational age are notper se indicators of good or ill health, but they are useful tools for defining the level of biological maturity of the foetus or child. In terms of health, it is widely observed that very preterm (less than 28 weeks of gestation) or very low birthweight infants are, if they survive, at high risk of handicap and other impairments (Stewart et al., 1981; Mc Cormick, 1985; Milner and Greenough, 1988). Even minor handicap (for example, minor brain damage) may seriously impair the children's quality of life. In any case they represent important social and economic expenses at the family and societal levels (Sinclair, 1986).

In spite of its higher specificity as indicator of immaturity, gestational age is in most data bases considered to be less accurate than birthweight. The latter is thus

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72 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

preferred to evaluate the magnitude of the population at risk ofneurodevelopmental handicaps. The recommendation as a criterion for such risk is the proportion of infants weighing less than 1,500 g.

5.2. EVOLUTION OF LOW= AND VERY LOW BIRTHWEIGHT BIRTHS IN EUROPE

Beside theory and recommendations, the differences over time and between coun- tries in the incidence of very low birthweight births (< 1,500 g) are probably mostly due to differences in legal or de facto definitions concerning birth registration. The impact of the availability and accessibility of adequate neonatal intensive care, which is chiefly required by very low birthweight infants, was already mentioned. For instance, the very high incidence of those frail infants in Poland (Table 2) underestimates in fact the real incidence of infants weighing less than 1,000 g at birth. Actually a minimum 24 hours survival is required for official registration of newborns weighing less than 1,001 g in Poland. If they do not survive, they are registered in a separate category called 'Non viable births with signs of life' and published accordingly but are not included in the official infant mortality figures. Survival bias in the official recognition of births weighing less than 1,000 g in Poland also causes the comparative low (official) mortality rate of this birthweight category (Table 3a, 3b).

5.3. BIRTHWEIGHT SPECIFIC MORTALITY RATES

The observed discrepancies and the evidence of selective underregistration of the lowest birthweight (liveborn) infants, enhance the need to seek for comparable indicators. In this case, the calculation of birthweight specific mortality rates offers a solution for the comparison of infant mortality levels, the more for early neonatal mortality (Table 3a, 3b).

A closer examination of the contents of the registration forms (live birth, still- birth and death records) and of the data processing methods, namely the birth and death record linkages routinely or occasionally performed by the National Statis- tical Institutes, gave some indications as to the feasability of producing adequate and comparable perinatal statistics. It is considered here that, given the observed heterogeneity of birth definitions across countries, comparability depends on the possibility of standardizing mortality figures by birthweight or gestation duration. To do so, at least one of the two following requirements must be fulfilled: (i) if birthweight or gestation duration are recorded on the birth registration forms, then individual record linkage should be made between birth and death records, automatic procedures being preferred to manual linkage (Pinnelli, 1984); (ii) if record linkage is impossible (for legal or technical reasons), then the availability of birthweight or gestational age on all the relevant registration forms is required.

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INFANT HEALTH AND MORTALITY INDICATORS 73

TABLE 2. Very low birthweight (< 1500 g) and low birthweight (< 2500 g) births. Selected European countries. Incidence per 1000 live births

Country 1975 1980 1985 1990

< 1500 <2500 <1500 <2500 <1500 <2500 <1500 <2500

Austria - - 8.25 57.84 7.70 55.97

Belgium - 5.44 54.82 7. t0 58.90 6.99 60.82 a

Czechoslovakia (ex) 8.87 62.96 7.60 59.29 6.62 56.93 7.11 55.95

England and Wales - 7.80 65.29 b 9.00 68.13 9.82 67.47 c

GFR (ex) - 55.14 57.31 57.62 c

Hungary 17.41 111.76 15.33 103.54 15.07 99.38 12.94 92.73

Italy 8.44 d 67.41 ¢ 5.73 51.41 6.38 52.30 -

Poland f 8.45 72.78 8.53 75.79 9.01 77.80 9.82 80.53

(12.51) g (76.83) (12.80) (80.07) (12.73)(81.52) (13.30)(84.02)

Portugal - 4.81 48.48 5.77 53.99 6.36 56.36

Switzerland - 5.27 51.32 h 5.78 50.82 i 6.57 51.27

Source: Vital Registration. a 1988 b 1981 ¢ 1989 d <1550 g (1973) e <2550 g (1973) e <1501 g and <2501 g g in brackets, including the "non viable births with signs of life" h 1979--81 i 1986.

Only 12 out of 27 European countries had the ability in 1991 to produce standardized perinatal mortality figures which follow the WHO recommendations for international comparisons (Gourbin and Masuy-Stroobant, 1993).

Attempts to establish standard birthweight distributions within each country, and methods for adjusting birthweight distributions (Z adjustment), in order to compare mortality levels on this basis are expanding and may provide interesting results (Rooth, 1980; Wilcox and Russel, 1983, 1986).

Finally, the increasing availability since the late seventies of population-based (vital registration, medical birth registries) health indicators such as birthweight or gestational age, offer the possibility of evaluating and monitoring the evolution of physical frailty in infancy. Other indicators like the psychomotor development of the child, its ability to attend 'normal' education, etc. although theoretically and potentially more specific, are at present rarely collected on a comparable and systematic way. Sample sizes are usually small and unrepresentative (Escobar et al., 1991).

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74 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

TABLE3a. Early neonatal mortality risks (per 1000 live births) by birthweight. Selected European countries - 1985

Country Birthweight (grams) Total early Total infant <1500 1500-2499 2500-3499 3500+ neonatal mortality mortality

Austria 338.42 22.60 1.90 1.33 5.49 11.17 Belgium 247.83 24.79 2.05 1.06 4.72 9.90 Czechoslovakia a (ex) 627.21 68.93 3.88 1.76 10.40 13.37 England and Wales 231.36 14.68 1.50 0.85 4.35 9.36 Hungary 504.59 33.71 2.86 1.79 12.70 20.40 Italy 456.84 39.60 2.42 1.35 6.84 10.55 Poland b 398.59 56.21 5.99 2.34 10.42 18.48

(598.98)c (14.09) (22.11)

Source: Vital Registration. a 1986 b weight' classes <1501, 1501-2500, 2501-3000, 3001 + c in brackets, including "non viable births with signs of life"

TABLE 3b. Early neonatal mortality risks (per 1000 live births) by birthweight. Selected European countries - 1990

Country Birthweight (grams) Total early Total infant <1500 1500-2499 2500-3499 3500+ neonatal mortality mortality

Austria 189.38 18.32 1.24 0.64 3.28 7.84 Belgium a 203.84 21.03 1.98 1.03 4.14 9.01 Czechoslovakia (ex) 579.44 44.74 3.55 1.37 8.85 11.25 England and Wales b 182.53 9.11 1.07 0.78 3.66 8A4 Hungary 397.91 22.94 2.09 1.56 8.73 14.82 Poland c 336.63 44.33 3.18 1.84 8.97 16.01

(510.40) a (12.41) (19.42)

Source: Vital Registration. a 1988 b 1989

c weight classes <1501, 1501-2500, 2501-3000, 3001 + d in brackets, including "non viable births with signs of life"

6. S o c i a l inequalities in infant health and m o r t a l i t y . A n indicator of unequal social and economic development?

In fan t m o r t a l i t y t o d a y is b e l o w 1% in m o s t W e s t e m E u r o p e a n coun t r i e s . Th i s

p r o g r e s s is i m p r e s s i v e bu t is it en t i r e ly s a t i s f ac to ry? A b i o l o g i c a l t h r e s h o l d o f

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INFANT HEALTH AND MORTALITY INDICATORS 75

unavoidable mortality has still not been reached: intemational differences and social differences within countries still persist. A further reduction is thus possible even in the lowest infant mortality countries, the objective being the level expe- rienced by the highest social classes within each country through a reduction of what is considered to be an inequity (Illsley, 1990). The importance of the social inequalities approach is further reinforced if one considers that similar inequalities are identified for health indicators such as prematurity, quality of life in infancy or the ability to overcome handicaps later in childhood.

To monitor and evaluate public health measures adopted to these ends, the validity of the measurement of social inequalities should be assessed. Once again, lack of consistency and comparability over time and space is observed in the methods currently used to distribute births into appropriate social classes.

6.1. CONSISTENCY OF SOCIAL CLASS INDICATORS

People lower down the social scale are less likely to use the preventive and curative care provided (Buekens et al., 1993). Numerous epidemiological studies show that similar social class differences are found in many indicators of the quality of the mothers' preventive behaviour, including planning of the baby, adequacy of antenatal clinic attendance, smoking and alcohol drinking during pregnancy (Masuy-Stroobant, 1988; 1989). Similar social inequalities are observed in the mothers' health status, such as nutritional status and previous adverse pregnancy outcome. Consequently, social inequalities in mortality begin long before the birth itself, and a thorough explanation must consider the whole reproduction process from beginning to end and the complex interactions between social and biological factors, including matemal characteristics (Alexander and Keirse, 1989).

The role of social class in such health/mortality inequalities is usually estab- lished by reference to the socio-occupational characteristics of the father. The first population-based analysis of this type was made in the United Kingdom in 1911 (Morris and Heady, 1955). The occupations of the household heads were grouped into five 'social classes'. Revised around each census period (every 10 years), this classification originally referred exclusively to the fathers' economic activity. The social class approach is very common in socio-epidemiological literature, but the exact role which social factors play in the causal process is far from clear: it could be risk factor, confounding, cause or intermediate variable (Liberatos et al., 1988).

Part of the vagueness of the social class effect is linked to its complexity. In theory the concept of social class is a compound of at least three dimensions usually measured by education, income and economic activity. Although partly interrelated, each of these components seems to have an independent effect on health and mortality (Abramson et al., 1982). The importance of inequalities will often vary according to the specific social class indicators used and whether a single indicator or a compound index is preferred.

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76 GODELIEVE MASUY-STROOBANT AND CATHERINE GOURBIN

Through its indicators, the social class concept is often reduced to its single economic dimension: occupation of the head of the household (Botting and Macfarlane, 1992; Cnattingius and Haglund, 1992), the ownership of selected con- sumer goods or according t o income (Kadin 1982). This oversimplification suffers from theoretical shortcomings, and is probably far from adequate and specific in a general European context where maternal and child health services are currently free of charge. Lack of specificity also in the traditional reference to the fathers' status and occupation, even though mothers are chiefly concerned with the decision to use adequate care. Furthermore, occupational and socio-economic scales con- structed for men are often meaningless for women: their respective occupational structures differ and in most cases women receive less income for a specific occu- pation then men do. The changing structure of the family, with a sharp increase of out-of-wedlock births and instability of unions are further sources of distortions where the mothers' status is to be identified by her partner's (if there is a partner). Furthermore, social advantages for pregnant or nursing mothers are in many coun- tries specifically linked to their professional activity (maternity leave, protection of pregnant women at work, etc.). The changing relationship over time between the mother's economic activity and her pregnancy outcome (mortality, prematurity, stillbirth rate) (Saurel-Cubizolles and Kaminski, 1982a; Masuy-Stroobant, 1990) is only one of the many arguments for a reconsideration of maternal socio-economic characteristics in infant health and mortality studies, even if exclusive references to the father are less frequent in recent literature.

The level of education of the mother, seldom considered in socio-epidemiolog- ical studies, seems both theoretically (Caldwell, 1979) and conceptually more appropriate as a social indicator in this field, given that education is a more specific indicator of the maternal capacity to understand and adopt recommended preventive behaviour in general and to use medical care adequately (Masuy-Stroobant, 1988; Saurel-Cubizolles et al., 1982b; Blondel et al., 1982, Boltanski, 1969). Beyond its theoretical interest, the mother's education, compared with the fathers' occupation, is easy to collect by interviewing the concerned person during clinic attendance, is stable over time and is a unique and valid indicator of social inequalities in infant health and mortality.

6.2. SOCIAL INEQUALITIES IN INFANT HEALTH AND MORTALITY. AVA/LABLE DATA

IN EUROPE

Three major periods need to be distinguished conceming the content and the forms used for vital registration and, consequently, the availability of data which permit the calculation of infant mortality figures by social characteristics:

- Up till the Second World War, social information was rarely recorded. Only sex and legitimacy of the infant were usually recorded on both birth and death forms. Record linkage with other administrative data (censuses for instance)

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INFANT HEALTH AND MORTALITY INDICATORS 77

in order to include the items related to the social class position of the infant's family were exceptional.

- Around 1939-1946, an increasing interest in fertility analyses and policies led to an enrichment of the birth records (including frequently stillbirths), espe- cially in the respect of the socio-demographic characteristics of both parents, while infant deaths were still registered on general death forms without any specific information on the infant's social background. Besides the legitimacy component, evaluation of social inequalities in infant mortality could only be obtained through record linkages (birth-infant death). Such linkages were first performed occasionallly for research purposes in the years 1973-1975. Later on (mostly during the eighties) linkages started to be routinely performed by the National Statistical Institutes in a number of countries.

- An important step was put forward by the end of the seventies and the begin- ning of the eighties when a number of European countries decided to include medical information in their birth records and, simultaneously to introduce either a specific form for infant or neonatal deaths or to add specific informa- tion for infant deaths on the general death form. At this stage, an increasing number of countries were able to produce figures on social components of 10w birthweight or preterm births and infant mortality rates stav.dardized by birthweight or gestational age, by social class or other indicators of the social position of the infant's mother or parents.

In addition to the possibility of producing standardized perinatal or infant mor- tality figures, 11 European countries collect at least one social class indicator at birth and sometimes at death registration. For the calculation of comparable (stan- dardized) mortality rates by social class, similar information should be available on birth and death records; routinely performed record linkage may provide the information for the deceased if it is only collected at birth registration (Table 4).

In the meantime, health ministries were also interested in collecting more med- ical data related to delivery in order to monitor the quality of obstetric care and later of neonatal care. Although they contain much interesting medical information, the medical birth registries are not always able to ensure complete coverage of infant deaths and they are, up till recently, very poor in collecting specific social data. In some cases however (Denmark, Finland, Iceland and Scotland) linkages with vital registration files may compensate for the deficiencies in socio-demographic information.

6.3. SOCIAL INEQUALITIES IN PERINATAL MORTALITY. FACTS AND FIGURES

Despite its limitations perinatal mortality figures were preferred for the international comparisons of social inequalities, partly because of their availability, but especially because of their ability to overcome some of the social and international differences in the legal and de facto viability criteria.

Page 16: Infant health and mortality indicators

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Before proceeding to international comparisons (Table 5) in this field one has to consider the limitations caused by differences in vital registration definitions, where stillbirths are registered from 26 weeks gestation in Finland and Italy, 35 cm body length in Austria and 28 weeks gestation in the other countries. The social class indicators and scales are even more difficult to compare: in England and Wales they refer to the fathers' social class and are limited to legitimate births and to illegitimate births registered by both parents, in Scotland, social class for illegitimate births is derived from the mothers' characteristics, in Belgium, education and income are not recorded at birth, hence social class indicators refer mainly to occupational categories. The social meaning of the mothers' economic activity varies from one country to another, depending partly on access to adequate day-care centres for the babies of the working mothers: in Austria, they are not organized at the country level, in Belgium day-care centres and mothers are supervised by the maternal and child health system and are even financially supported by the state.

Whatever the country, the period and the general level of perinatal mortality, children of unmarried, less educated and unemployed mothers are at higher risk. The relative risk of lowest to highest social class children reaches at least 1.5. In the countries (Italy, England and Wales, Scotland) where figures are available at the beginning and the end of the eighties, the relative risks are decreasing for illegitimacy but are rather stable for the other social variables in spite of a general decrease in perinatal mortality within each social group. One has also to consider the relative weight of the different social groups within the general population. Extreme (high or low-level) groups tend to be far less numerous than the medium level ones, hence differences and inequalities may be exaggerated.

7. Conclusions

Geographical and temporal comparisons of infant health or mortality indicators in Europe are still difficult to make. Given the specific characteristics of the de facto infant mortality today, infant deaths tend to be concentrated more and more in the very early days and hours of life and the relative weight of very small (low birthweight and preterm) infants is growing. With the advances in neonatal intensive care techniques, survival of very low birthweight babies (less than 1,500 g) and very preterm babies (less than 28 weeks gestation duration) is constantly improving. Consequently, medical viability criteria and legal rules defining the registration of births may no longer coincide. Moreover, in spite of a general tendency towards the adoption of common definitions for vital registration of live and stillbirths all over Europe, there are still significant differences and their impact on the comparability of the infant mortality figures derived from them is presumably rising (Gourbin and Masuy-Stroobant, 1993).

The assumption that further improvements in survival rates imply per se better health in early infancy must be discussed when more and more very small infants are able to survive. The increasing availability of birthweight or gestational age

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80 GODELIEVE M A S U Y - S T R O O B A N T A N D CATHERINE GOURBIN

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INFANT HEALTH AND MORTALITY INDICATORS 81

through vital registration provides some information on the incidence of children at risk, but they refer to the situation at birth. Further and more specific indicators are thus needed for monitoring health in early childhood.

Beside the choice of appropriate social class indicators, the comparability over time and place of social inequalities in health has seldom been studied from a methodological point of view (Carr-Hill, 1987; Wagstaff et al., 1991). Given the political importance attached to both the level and social inequality of infant mor- tality (Reid, 1986), especially when they are claimed to be increasing (Townsend and Davidson, 1988), there is an urgent need to evaluate systematically the appro- priateness of the measures of the size of the observed inequalities. A review of the existing methods has recently be made (Wagstaff et al., 1991), but their sensitivity to applied situations has not yet been studied. But, whatever the quality of the method, appropriate, comparable and updated data on social class and pregnancy outcome, birthweight, gestational age or infant death are needed. A recent survey conducted in 1991 (Gourbin and Masuy-Stroobant, 1993) showed that only 11 out of the 27 participating European countries had the capacity to produce adequate figures, but their comparability is still to be evaluated.

Acknowledgements

This research, part of a larger programme on The Social and Regional Inequalities in Health and Mortality in Europe, is funded by the Minist~re de la Communaut6 Franqaise de Belgique, A.C. Grant number 89/94--138.

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Correspondence to: Godelieve Masuy-Stroobant, Institut de D6mographie, Universit6 Catholique de Louvain, 1 Place Montesquieu, bte 17, B-1348 Louvain-la-Neuve, Belgium