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Environmental Factors Implicated in the Causation of Adverse Pregnancy Outcome Elizabeth Westerlund Triche, PhD, and Nazli Hossain, MBBS, FCPS Adverse pregnancy outcome from environmental factors may include congenital anomalies, increased risk for miscarriage, preterm delivery, intrauterine growth restriction, and still birth. Apart from adverse pregnancy outcome, there may be effects on the other reproduc- tive functions, like menstrual disorders and infertility. Environmental factors which have been implicated in adverse pregnancy outcome include smoking, video display terminals, anesthetic gases, antineoplastic drugs, and exposure to lead, selenium, and inorganic mercury. Among these, cigarette smoking during pregnancy has been the leading environ- mental factor for adverse pregnancy outcome. Cigarette smoking during pregnancy con- tinues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g). Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Similarly, air pollution, pesticide exposure, and stress have also been associated with low birth weight and preterm delivery. This review gives an overview of the importance of environmental factors in adverse pregnancy outcome. Semin Perinatol 31:240-242 © 2007 Elsevier Inc. All rights reserved. KEYWORDS nicotine, low birth weight, pregnancy, neuroteratogen, mercury, pesticide, video display terminals Smoking The harmful effects of smoking are well established. None- theless, smoking rates among women have remained at high levels for the past 25 years. Despite warnings of the negative consequences of smoking, approximately 20% to 25% of adult women in the United States are smokers, 1 with even higher rates among younger women and women of lower socioeconomic status. 2 Concomitant increases in cancer, heart disease, and other diseases directly attributable to smoking have been observed in women. Women of child- bearing age represent a large proportion of all female smok- ers. Smoking during pregnancy is associated with a number of poor birth outcomes, including low birth weight, intra- uterine growth retardation, 3 placental problems, 4 preterm delivery, and spontaneous abortion. 5,6 In Connecticut alone, there were 4381 preterm births and 3200 low-birth weight babies born in the year 2000 (CT Registration Reports, pre- liminary data). Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants (LBW). These infants weigh an average of 150 to 250 g less than infants born to nonsmoking mothers. 7 In addition to the hazards of smoking for the mother, exposure to environmen- tal tobacco smoke is a risk factor for Sudden Infant Death Syndrome (SIDS), ear infections, asthma, and other respira- tory conditions in the infant. 8 Maternal smoking during preg- nancy has not only detrimental effect on placental function, nicotine also crosses the placenta to act as neuroteratogen. It interferes with the fetal development, specifically affecting the nervous system. In utero, nicotine targets the fetal nico- tinic acetyl choline receptors in the brain, to change the pat- tern of cell proliferation and differentiation. This results in cell loss and neuronal damage. This in turn has been associ- ated with risks of cognitive and auditory processing deficits and effects on social behavior. 9,10 Metals Lead, mercury, nickel, and manganese have been associated with poor reproductive outcome. An increased risk for spon- taneous abortion has been associated with low levels of lead exposure. This was illustrated in a nested case-control study in which women who were followed prospectively during Yale Women & Children’s Center for Blood Disorders, Yale University School of Medicine, New Haven, CT. Address reprint requests to Elizabeth Westerlund Triche, PhD, Yale Univer- sity School of Medicine, 60 College St., New Haven, CT 06510. E-mail: [email protected]. 240 0146-0005/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.semperi.2007.07.013

Environmental Factors Implicated in the Causation of Adverse Pregnancy Outcome

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Page 1: Environmental Factors Implicated in the Causation of Adverse Pregnancy Outcome

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nvironmental Factors Implicated in theausation of Adverse Pregnancy Outcome

lizabeth Westerlund Triche, PhD, and Nazli Hossain, MBBS, FCPS

Adverse pregnancy outcome from environmental factors may include congenital anomalies,increased risk for miscarriage, preterm delivery, intrauterine growth restriction, and stillbirth. Apart from adverse pregnancy outcome, there may be effects on the other reproduc-tive functions, like menstrual disorders and infertility. Environmental factors which havebeen implicated in adverse pregnancy outcome include smoking, video display terminals,anesthetic gases, antineoplastic drugs, and exposure to lead, selenium, and inorganicmercury. Among these, cigarette smoking during pregnancy has been the leading environ-mental factor for adverse pregnancy outcome. Cigarette smoking during pregnancy con-tinues to be a significant public health concern. Maternal smoking during pregnancy hasbeen associated with low birth weight (<2500 g). Mothers who smoke during pregnancyare twice as likely to give birth to low-birth weight infants. Similarly, air pollution, pesticideexposure, and stress have also been associated with low birth weight and preterm delivery.This review gives an overview of the importance of environmental factors in adversepregnancy outcome.Semin Perinatol 31:240-242 © 2007 Elsevier Inc. All rights reserved.

KEYWORDS nicotine, low birth weight, pregnancy, neuroteratogen, mercury, pesticide, videodisplay terminals

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mokinghe harmful effects of smoking are well established. None-

heless, smoking rates among women have remained at highevels for the past 25 years. Despite warnings of the negativeonsequences of smoking, approximately 20% to 25% ofdult women in the United States are smokers,1 with evenigher rates among younger women and women of lowerocioeconomic status.2 Concomitant increases in cancer,eart disease, and other diseases directly attributable tomoking have been observed in women. Women of child-earing age represent a large proportion of all female smok-rs. Smoking during pregnancy is associated with a numberf poor birth outcomes, including low birth weight, intra-terine growth retardation,3 placental problems,4 pretermelivery, and spontaneous abortion.5,6 In Connecticut alone,here were 4381 preterm births and 3200 low-birth weightabies born in the year 2000 (CT Registration Reports, pre-

iminary data). Mothers who smoke during pregnancy are

ale Women & Children’s Center for Blood Disorders, Yale UniversitySchool of Medicine, New Haven, CT.

ddress reprint requests to Elizabeth Westerlund Triche, PhD, Yale Univer-sity School of Medicine, 60 College St., New Haven, CT 06510. E-mail:

[email protected].

40 0146-0005/07/$-see front matter © 2007 Elsevier Inc. All rights reserved.doi:10.1053/j.semperi.2007.07.013

wice as likely to give birth to low-birth weight infantsLBW). These infants weigh an average of 150 to 250 g lesshan infants born to nonsmoking mothers.7 In addition to theazards of smoking for the mother, exposure to environmen-al tobacco smoke is a risk factor for Sudden Infant Deathyndrome (SIDS), ear infections, asthma, and other respira-ory conditions in the infant.8 Maternal smoking during preg-ancy has not only detrimental effect on placental function,icotine also crosses the placenta to act as neuroteratogen. It

nterferes with the fetal development, specifically affectinghe nervous system. In utero, nicotine targets the fetal nico-inic acetyl choline receptors in the brain, to change the pat-ern of cell proliferation and differentiation. This results inell loss and neuronal damage. This in turn has been associ-ted with risks of cognitive and auditory processing deficitsnd effects on social behavior.9,10

etalsead, mercury, nickel, and manganese have been associatedith poor reproductive outcome. An increased risk for spon-

aneous abortion has been associated with low levels of leadxposure. This was illustrated in a nested case-control study

n which women who were followed prospectively during
Page 2: Environmental Factors Implicated in the Causation of Adverse Pregnancy Outcome

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Environment and adverse pregnancy outcome 241

regnancy had an odds ratio for spontaneous abortion of 1.895% CI 1.1–3.1) for every 5 �g/dL increase in blood leadevel (range 5 to 20 �g/dL)11 Women exposed to lead includehose in the paint industry or artists and painters. Leadeadily crosses the placenta, and has been found to haveeratogenic effects as well and is known to affect the hor-onal environment needed to maintain the pregnancy. Leadas also been found to be associated with still births in hu-ans. Women at risk of lead exposure should be monitored

or blood lead levels before becoming pregnant. Mercuryxposure has been identified in dental assistants preparingmalgams. This has been linked to spontaneous abortion asell as reduced fertility.12

nhalational Anestheticsvidence supporting inhalational anesthetics and adverseregnancy outcome is weak. Recent studies from Westernountries are often negative, emphasizing the importance ofreventive measures in reducing the risk.13 One study didnd increased risk for infertility in dental assistants exposedo higher concentration of nitrous oxide.14 Limitation of ex-osure should be considered for workers where operatingooms are not properly scavenged.

rganic Solventsomen working in clothing, textile, paint, and plastic indus-

ries and health care professionals are exposed to organicolvents. Khattak and coworkers in a prospective study dem-nstrated that women exposed occupationally to organic sol-ents had a 13-fold risk of major malformations as well as anncreased risk for miscarriages in previous pregnancies whileorking with organic solvents.15

ir Pollutiont has been associated with congenital birth defects, as well asith low birth weight and intrauterine growth restriction.

edrychowski and coworkers surveyed pregnant women inoland exposed to fine particulate matter (PM 25) and as-essed its effect on birth outcomes. They showed an associa-ion with low birth weight and reduced head circumferencen children born to the above group of women.16 Air pollu-ion has also been associated with congenital cardiovascularirth defects.17 In a meta analysis on air pollution and preg-ancy outcome, the author concluded that there is a causal

ink between air pollution and low birth weight.18 For pre-erm births and intrauterine growth retardation (IUGR), theyoncluded that the evidence as yet is insufficient to inferausality, but the available evidence justifies further studies.

esticide Workersregnant women working in the agricultural fields and land-cape artists are at risk for pesticide exposure. The epidemi-logical literature does suggest increased risk of spontaneous

iscarriages, low birth weight, and preterm delivery in green r

ouse workers.13 Other potential effects of exposure includenfertility and reduced fecundity in women of reproductivege group. Exposed women should have urinary levels quan-itated during pregnancy.

adiationxposure to ionizing radiation during periconceptional periodnd during early gestation has been associated with congenitalefects and risks of childhood cancer. Generally speaking,owadays state laws prescribe that pregnant women shoulde protected from doses �1 mSv throughout pregnancy.nother common cause of concern is nonionizing radiation,

n particular electromagnetic field waves, as in video displayerminals, daily exposure to mobile phones, heated beds,lectric blankets, and health professionals using diagnosticnd therapeutic devices.

Video display terminals do not emit ionizing radiations,ut they do emit electromagnetic radiations. Their use duringregnancy has not been associated with adverse pregnancyutcome or with any teratogenic effects. A recent meta anal-sis on the subject did not find any increased risk for spon-aneous abortion, low birth weight, and prematurity associ-ted with electro magnetic radiations.19 Long-term use haseen linked with carpal tunnel syndrome, due to the anglingffect on the wrist.

tresshe impact of stress has been evaluated after World Tradeenter (WTC) disaster, in a number of publications. In aorkgroup Report on Consequences of the WTC disaster,

he Mount Sinai cohort, found a 2-fold increased risk ofmall-for-gestational-age (SGA) infants, defined as infantsith a birth weight below the tenth percentile for gestational

ge.20 Maternal stress has been found to be associated withirth defects, low birth weight, preterm delivery, and earlynset preeclampsia. A recent population-based case controltudy found a positive association between maternal stress (2onths before and after conception) and cleft lip, cleft palate,

nd transposition of great vessels.21 In a case control study,ob stress and chronic exposure to work has been found to beinked with preterm deliveries. This association is found to bereater in black women.22 Increased job strain in the first 20eeks of pregnancy has been linked to increased incidence ofreeclampsia. The authors attributed it to increased release ofatecholamines, associated with increased job stress (OR �.1 95% CI 1.1-4.1).23 Another case control study showedhat the risk of having a small-for-gestational-age (SGA) in-ant increased with an irregular or shift-work schedule alone,r when combined with the following occupational condi-ions: night hours, irregular or shift-work schedule, standing,ifting loads, noise, and high psychological demand com-ined with low social support (P value 0.004). Elimination ofhe conditions before 24 weeks of pregnancy brought the

isks close to those of unexposed women.24
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242 N. Hossain and E.W. Triche

hysical Stresshese include long hours of standing, bending, lifting heavyeights, and long week hours of work. The adverse preg-ancy outcomes associated with it include SGA, low birtheight, and preterm delivery. SGA is found to be associatedith a work �50 hours/week, and with work involving

tanding �7 hours/day. Physical strenuous work, combinedith other factors like stress and poor antenatal care, might

ncrease the risk for adverse pregnancy outcome.

onclusionnvironmental factors do play an important role in maternalealth. They make an important contribution toward placen-al problems like low birth weight and intrauterine growthestriction, as well as have long-term effects on neuronal andehavioral development in adult life.

eferences1. Arnett DK, Sprafka JM, McGovern PG, et al: Trends in cigarette smok-

ing: the Minnesota Heart Survey, 1980 through 1992. Am J PublicHealth 88:1230-1233, 1998

2. Mullen PD: How can more smoking suspension during pregnancy be-come lifelong abstinence? Lessons learned about predictors, interven-tions, and gaps in our accumulated knowledge. Nicotine Tob Res 6:S217-S238, 2004 (suppl 2)

3. Horta BL, Victora CG, Menezes AM, et al: Low birthweight, pretermbirths and intrauterine growth retardation in relation to maternalsmoking. Paediatr Perinat Epidemiol 11:140-151, 1997

4. Raymond EG, Mills JL: Placental abruption. Maternal risk factors andassociated fetal conditions. Acta Obstet Gynecol Scand 72:633-639,1993

5. Miller HC, Hassanein K, Hensleigh PA: Fetal growth retardation inrelation to maternal smoking and weight gain in pregnancy. Am JObstet Gynecol 125:55-60, 1976

6. Raymond EG, Cnattingius S, Kiely JL: Effects of maternal age, parity,and smoking on the risk of stillbirth. Br J Obstet Gynaecol 101:301-306, 1994

7. Andres RL, Day MC: Perinatal complications associated with maternaltobacco use. Semin Neonatol 5:231-241, 2000

8. Dybing E, Sanner T: Passive smoking, sudden infant death syn-drome (SIDS) and childhood infections. Hum Exp Toxicol 18:202-

205, 1999

9. Jacobsen LK, Slotkin TA, Mencl WE, et al: Gender-specific effects ofprenatal and adolescent exposure to tobacco smoke on auditory andvisual attention. Neuropsychopharmacology 2007, in press

0. Toro R, Leonard G, Lerner JV, et al: Prenatal exposure to maternalcigarette smoking and the adolescent cerebral cortex. Neuropsychop-harmacology 2007, in press

1. Borja-Aburto VH, Hertz-Picciotto I, Rojas Lopez M, et al: Blood leadlevels measured prospectively and risk of spontaneous abortion. Am JEpidemiol 150:590-597, 1999

2. Rowland AS, Baird DD, Weinberg CR, et al: The effect of occupationalexposure to mercury vapour on the fertility of female dental assistants.Occup Environ Med 51:28-34, 1994

3. Figa-Talamanca I: Occupational risk factors and reproductive health ofwomen. Occup Med (Lond) 56:521-531, 2006

4. Rowland AS, Baird DD, Weinberg CR, et al: Reduced fertility amongwomen employed as dental assistants exposed to high levels of nitrousoxide. N Engl J Med 327:993-997, 1992

5. Khattak S, K-Moghtader G, McMartin K, et al: Pregnancy outcomefollowing gestational exposure to organic solvents: a prospective con-trolled study. JAMA 281:1106-1109, 1999

6. Jedrychowski W, Bendkowska I, Flak E, et al: Estimated risk for alteredfetal growth resulting from exposure to fine particles during pregnancy:an epidemiologic prospective cohort study in Poland. Environ HealthPerspect 112:1398-1402, 2004

7. Ritz B, Yu F, Fruin S, et al: Ambient air pollution and risk of birthdefects in Southern California. Am J Epidemiol 155:17-25, 2002

8. Sram RJ, Binkova B, Dejmek J, et al: Ambient air pollution and preg-nancy outcomes: a review of the literature. Environ Health Perspect113:375-382, 2005

9. Shaw GM: Adverse human reproductive outcomes and electromagneticfields: a brief summary of the epidemiologic literature. Bioelectromag-netics Suppl 5:S5-S18, 2001

0. Landrigan PJ, Lioy PJ, Thurston G, et al: NIEHS World Trade CenterWorking Group. Health and environmental consequences of the WorldTrade Center disaster. Environ Health Perspect 112:731-739, 2004(Review)

1. Carmichael SL, Shaw GM, Yang W, et al: Maternal stressful life eventsand risks of birth defects. Epidemiology 18:356-361, 2007

2. Brett KM, Strogatz DS, Savitz DA: Employment, job strain, and pretermdelivery among women in North Carolina. Am J Public Health 87:199-204, 1997

3. Marcoux S, Berube S, Brisson C, et al: Job strain and pregnancy-in-duced hypertension. Epidemiology 10:376-382, 1999

4. Croteau A, Marcoux S, Brisson C: Work activity in pregnancy, preven-tive measures, and the risk of delivering a small-for-gestational-age

infant. Am J Public Health 96:846-855, 2006