Maternal Smoking & Congenital Defects

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Written and compiled by Wanda Hamilton

Numerous studies have been done over the years on the relationship of maternal smoking during pregnancy and congenital defects, and without question the scientific consensus is that maternal smoking is not associated with either neurological or physical congenital defects. In fact, many studies have indicated a slight decrease in the rates of congenital defects for infants of smoking mothers. For example, study after study has shown that the risks of having an infant with Down's syndrome are lower for smoking mothers.

"There was no evidence of an association between any congenital defect and smoking."
McDonald AD, Armstrong BG, Sloan M, "Cigarette, alcohol, and coffee consumption and congenital defects," American Journal of Public Health, Jan l992; 82(1):91-3. [CDC bib, l992-93, p. 66]

". . .found no increased risk [of congenital malformations] for infants of smokers." "When adjusted for potential confounders the odds ratio for congenital malformation in the infants of women who smoked during pregnancy was not increased (odds ratio = 0.98)." A slightly lower risk for infants of smoking mothers.

Malloy MH, Kleinman JC, et al. "Maternal smoking during pregnancy: no association with congenital malformations in Missouri 1980-83," American Journal of Public Health, Sep l989, 79(9):1243-6.

"Neither maternal nor paternal smoking habits were significantly associated with the occurrence of congenital malformations." In this study the "incidence of congenital anomalies was examined by the level of maternal and paternal smoking during pregnancy for 17,152 infants."

Seidman DS, Ever-Hadani P, Gale R. Obstetrics and Gynecology, Dec l990; 76(6):1046-1050.

"Maternal smoking habits in 67,609 singleton pregnancies were examined. The overall incidence of congenital malformations was 2.8% in both non-smokers and smokers. On analysing congenital defects according to individual systems there was no significant difference in the incidence of malformations according to the number of cigarettes smoked, except for neural tube defects. . . . This study suggests that maternal smoking does not have teratogenic effects in the offspring, except in the case of neural tube defects, where the effect is at most modest."

Evans DR, Newcombe RG, Campbell H. "Maternal smoking habits and congenital malformations: a population study," British Medical Journal, Jul 21 l979; 2(6183):171-173.

"Parental smoking was not associated with increased risks for neural tube defects."

Wasserman CR, Shaw GM, O'Malley CD, Tolarova MM, Lammer EJ. "Parental cigarette smoking and risk for congenital anomalies of the heart, neural tube, or limb," Teratology, Apr l996; 53(4):261-267.

"Statistically significant negative associations were found for ventricular septal defects (odds ratio, 0.5 [95% confidence interval 0.2-0.96]), hydroceles (0.7 [0.6-0.9]) clubfoot (0.7 [0.6-0.9], pigmented nevi (0.7 [0.6-0.9] hemangiomas (0.8 [0.7-0.98]) and Down syndrome (0.2 [0.1-0.9])." For all these congenital defects, the risks were significantly lower for the offspring of smoking mothers.

Shiono PH, Klebanoff MA, Berendes HW, "Congenital malformations and maternal smoking during pregnancy," Teratology, Aug l986; 34(1):65-71.

"Based on this large series of cases, maternal smoking during pregnancy does not appear to increase the risk of oral clefts."

Werler MM, Lammer EJ, Rosenberg L, Mitchell AA, "Maternal cigarette smoking during pregnancy in relation to oral clefts," Am J Epidemiol, Nov l990; 132(5):926-932.

"We did not find any association with Down's syndrome (RR = 0.8 95% CI 0.5-1.3) or any other malformation."

Van den Eeden SK, Karagas MR, Daling JR, Vaughan TL, "A case-control study of maternal smoking and congenital malformations," Paediatr Perinat Epidemiol, Apr l990; 4(2):147-155.

"Collectively, our results provide no evidence for an association between fetal Down's syndrome and smoking. Other published studies found a deficit of smokers among women who had pregnancies associated with Down's syndrome."

Cuckle HS, Alberman E, Wald NJ, Royston P, Knight G, "Maternal smoking habits and Down's syndrome," Prenatal DiagnosisSep l990, 10(9); 561-7.

"The risk of cardiovascular malformations was not associated with maternal smoking."

Tikkanen J, Heinonen OP, "Maternal exposure to chemical and physical factors during pregnancy and cardiovascular malformations in the offspring," Teratology, Jun l991; 43(6): 591-600. "No statistically significant differences were found in the frequencies of CAs [chromosome aberrations] between non-smoking mothers (5.4% or 2.0% gaps excluded) and smoking mothers (3.5% or 1.0% gaps excluded)."
Salonen K, Lahdetie J, "No effect of maternal smoking in early pregnancy observed on chromosome aberrations in chorionic villus samples," Mutation Research, Feb l993; 298(4): 285-289.

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