Europ. J. Obstet. Gynec. reprod. Biol,, 19 (1985) 75-19

Elsevier

75

EJO 00152

Neurological morbidity in newborn twins

H. Kragt I, H.J. Huisjes ’ and B.C.L. Touwen ’

’ Department of Obstetncs and Gynecology, University Hospital Groningen, and 2 Department of

Developmental Neurology, Universiiy Hospital, 59 Oostersingel, 9713 EZ Groningen, The Netherlands

Accepted for publication 16 August 1984

KRAGT, H., HUISJES, H.J. and TOUWEN, B.C.L. (1985): Neurological morbidity in newborn twins.

Europ. J. Obstet. Gynec. reprod. Biol., 19, 75-79.

Forty-six twins were compared with an equal number of singletons, matched for gestational age.

birthweight and mode of delivery. The neurological findings in the neonatal period were similar in the

matched groups, but twins were significantly more often deviant than a large unselected sample of

singletons. It is concluded that both in twins and in singletons growth retardation, preterm birth and birth

trauma are important causes of neonatal neurological abnormality, but that twins are not more

susceptible to the effects of these variables than singletons.

developmental neurology; twins; nervous system; neonatal morbidity

Introduction

Both perinatal mortality and morbidity are higher in twins than in singletons. Depending on the obstetrical and neonatal care given, perinatal mortality of twins has been estimated to be 3-4-times that of singletons (Duncan et al., 1979; Mederas et al., (1979), and morbidity about 6-times (Ho and Wu, 1975). This poor fetal outcome in twin pregnancies is generally ascribed to an increased incidence of intrauterine growth retardation (IUGR), preterm birth (Bleker et al., 1979; Ho and Wu, 1975) and birth trauma (Van Bilderbeek, 1960). Other factors may be birth order, sex and asphyxia.

An unanswered question is whether twins are more vulnerable to these and other adverse pre- and perinatal circumstances than singletons. Therefore we compared neonatal neurological morbidity of twins with that of singletons matched for birthweight, gestational age and mode of delivery.

Patients and methods

Thirty pairs of twins were born in the Groningen University Hospital during the 1975-1978. Two fetuses were stillborn. The remaining 58 infants underwent neuro-

0028-2243/85/$03.30 0 1985 Elsevier Science Publishers B.V

TABLE I

Results of matching procedure

Twins Singletons

(n=46) (n =46)

Birthweight (g)

median

range

Gestational age (wk)

median

range

Weight centiles

< 10

210

Mode of delivery

vertex

vaginal breech

instrumental

caesarean section

2650 2675

1570-4ooo 1570-4200

38 38

32-41 32-41

10 11

36 3s

31

I

2

6

31

7

6

logical examination at term age, according to the technique described by Prechtl (1964, 1979). The results were classified in two ways: applying the diagnostic categories of ‘normal’, ‘suspect’ or ‘abnormal’, and using a neurological optimality score which rates the integrity of the central nervous system quantitatively. An extensive description of this approach has been given elsewhere (Jurgens-v.d. Zee et al., 1979). In short an infant was classified as abnormal when a circumscript neurological syndrome was found (e.g., hyperexcitability, hypotonia, a central hemi- syndrome or a peripheral plexus lesion). ‘Suspect’ meant that parts of a syndrome were present. The neurological optimality score is calculated by counting the neurological items representative of the central nervous system which fall within a predefined ‘optimal’ range. The number of items used was 60.

For each of the twins a singleton infant was sought in the files of the Groningen Perinatal Project, which contains data on 3162 children born and examined in the same period (see Huisjes et al., 1980). Matching criteria were gestational age, birthweight (plus or minus 200 g) and mode of delivery. Forty-six of the 58 available

twins could be successfully matched, and these are the subjects of the study (Table I). Birthweights of the 12 excluded infants ranged from 1750 to 2350 g, and their

gestational age varied from 32 to 38 wk; 2 of the infants were small for gestational age (< 10th percentile).

The x2 test was used for comparison of the groups of twins and singletons and the Wilcoxon test for comparing within pairs.

Results

Eight of the original group of 58 twins were neurologically suspect (14% and 34%). These percentages are higher than in the total group of 3162 singletons in the Perinatal Project, which were 5.1 and 21.4, respectively (Jurgens-v.d. Zee et al., 1979). The difference is statistically significant (x2 = 15.8, df= 2, P < 0.001).

TABLE II

Neurological findings in twins, related to birth order, sex and asphyxia

None of the differences is statistically significant

First twins

Second twins

Males

Females

PH umh.v. 2, 7.20

PH”~~.~. < 7.20

(n)

(26)

(20)

(21)

(25)

(37)

(4)

Neurological classification Neurological optimality score

Normal Suspect Abnormal Mean Median Range

15 7 4 55.1 57 44-59

10 8 2 55.3 55 48-60

8 10 3 55.7 55 48-60

17 5 3 55.7 57 44-59

21 11 6 55.0 55 44-60

2 2 0 55.1 56.5 52-56

TABLE III

Comparison of neonatal neurological diagnosis within matched twin-singleton pairs

Twins/singletons Normal Suspect Abnormal

Normal 15 -I 2

Suspect 11 4 1

Abnormal 5 1 0

Birth order, sex and asphyxia had no significant effect on neurological morbidity in the twin group (Table II), and therefore these variables were disregarded in the

comparison with matched singletons. In the group of 46 matched singletons three infants were neurologically abnormal

and 12 were suspect. Although the number of deviant infants is less than in the twin group, the difference is not statistically significant, either between the groups (x2 = 1.63, df= 1, P > 0.05) or within pairs (Table III; Wilcoxon: z = -1.37, P = 0.085). Using the neurological optimality score, as a group the twins scored insignificantly higher than the control group (M = 55.2 and 53.8 respectively; t = 1.94, P > 0.05). The only significant difference was found when comparing within pairs: twins scored higher in neurological optimality than singletons (Wilco-

xon: z = - 1.89, P = 0.029). Four of the six abnormal twins were severely hypotonic and hypokinetic, one had

a hemisyndrome and one a facialis asymmetry. Forty percent of the suspect twins

were hypertonic or hypokinetic, and 35% midly hypotonic or hypokinetic. It is known that these conditions are transient in most patients. In two of the abnormal

singletons, however, severe hypertonia was found, which is known to have a less favourable prognosis.

Discussion

Comparison of twins with a random subpopulation of singletons showed that twins are more often neurologically deviant in the neonatal period. When compared

78

with singletons matched for gestational age, birthweight and mode of delivery, the difference disappeared. Neurological diagnoses were even more favourable in twins than in singletons.

These findings may be explained by assuming that the nervous system of twins is not more, perhaps even less, susceptible to IUGR, preterm birth and complicated delivery than that of singletons. On the other hand, IUGR and preterm birth are of a different quality in singletons, inasmuch as IUGR is often caused by vascular disease and preterm birth by various complications of pregnancy. In twins IUGR predominantly is a consequence of sharing the supply-line and preterm birth is mostly caused by uterine distension. This difference could be substantiated by a comparison of the obstetrical optimality scores (Touwen et al., 1980) in the study and control group: the mean score in the twins was higher than in the singletons. Since the obstetrical optimality score is inversely related with neurological neonatal morbidity (Touwen et al., 1980) this indicates that the singletons run a higher risk than the twins.

The most likely explanation for our findings is that twins are not more vulnerable than singletons, and that, seemingly, similar circumstances in terms of birthweight,

gestational age and birth process are, in fact, more favourable in twins than in singletons. An effect of birth order, sex and acidemia on the neonatal neurological condition in twins could not be ascertained.

Acknowledgements

Our thanks are due to Dr. G.H.A. Visser for his support and to Mrs. A. Olinga for her technical assistance. This study is part of the Groningen Perinatal Project, which was supported in part by the Praeventiefonds and the Prinses Beatrixfonds.

References

Bleker, O.P., Breur, W. and Huidekoper, B.L. (1979): A study of birthweight, placentalweight and

mortality in twins as compared to singletons. Brit. J. Obstet. Gynec., St, 111-118.

Duncan, J.L.B., Gimh, B. and Wahab, H. (1979): Use of ultrasound and hormone assays in the diagnosis,

management, and outcome of twin pregnancy. Obstet. and Gynec., 53, 3, 367-372.

Huisjes, H.J., Touwen, B.C.L., Hoekstra, J., Woerden-Blanksma, J.T. van, Bierman-van Eendenburg,

M.E.C., Jurgens-v.d. Zee, A.D., Fidler, V.J. and Olinga, A.A. (1980): Obstetrical-neonatal neurological

relationship. A replication study. Europ. J. Obstet. Gynec. reprod. Biol., 7, 85-90.

Jurgens-v.d. Zee, A.D., Bierman-Van Eendenburg, M.E.C., Fidler, V.J., Olinga, A.A., Visch, J.H.,

Touwen, B.C.L. and Huisjes, H.J. (1979): Preterm birth, growth retardation and acidemia in relation

to neurological abnormality of the newborn. Early hum. Develop., 3, 141-154.

Mederas, A.L., Jonas, H.S., Stockbauer, J.W. and Donke, H.R. (1979): Perinatal deaths in twin

pregnancy. Amer. Obstet. Gynec., 134, 413-421. Prechtl, H.F.R. and Beintema, D.J. (1964): The neurological examination of the full term newborn infant.

In: Clinics in Developmental Medicine, 12. Heineman Medical Books, London.

Prechtl, H.F.R. (1979): The neurological examination of the full term newborn infant. In: Clinics in Developmental Medicine, No. 63, 2nd Edn. Spastics International Medical Publications. Heinemann

Medical Books, London.

Ho, S.K. and Wu, P.Y.K. (1975): Perinatal factors and neonatal morbidity in twin pregnancy. Amer. J.

Obstet. Gynec., 122, 979-987.

79

Touwen, B.C.L., Huisjes, H.J., Jurgens-v.d. Zee, A.D., Bierman-v. Eendenburg, M.E.C., Smirkovsky, M.

and Olinga, A.A. (1980): Obstetrical condition and neonatal neurological morbidity. An analysis with

the help of the optimality concept. Early hum. Develop., 4, 207-228.

Touwen, B.D.L. (1981): Recovery of neurobiological deviant infants. In: Functional Recovery from Brain

Damage. Editors: M.W. van Hof and G. Mohn. Development in Neuroscience, Vol. 13, pp. 77-94.

Elseviers Publishing Company, Amsterdam.

Van Bilderbeek, J. (1960): De obstetrische sterfte. In: Tweelingen, een klinisch verloskundige studie,

Thesis, pp. 82-103. Ruysendael, Amsterdam.