Folic acid supplementation and risk for fetal abdominal wall defects in China: results from a large population-based intervention cohort study.

Folic acid (FA) can reduce the risk for selected birth defects other than neural tube defects. We examined whether FA has preventive effects against fetal abdominal wall defects (AWD) in a unique intervention cohort in China. Birth outcomes of 247 831 singleton births from a population-based cohort study with detailed pre-conceptional FA intake information were collected in China in 1993-1996. Information on births at 20 complete gestational weeks, including live births, stillbirths and pregnancy terminations, and all structural birth defects regardless of gestational week were recorded. The birth prevalence of omphalocele, gastroschisis and total fetal AWD was classified by maternal FA supplementation. The prevalence of total AWD was 4·30 per 10 000 births among women who took FA compared with 13·46 per 10 000 births among those who did not take FA in northern China and 6·28 and 5·18 per 10 000 births, respectively, in southern China. The prevalence of omphalocele was 0·54 per 10 000 births among women who took FA compared with 3·74 per 10 000 births among those who did not take FA in northern China and 1·79 and 1·44 per 10 000 births, respectively, in southern China. FA supplementation significantly prevented total AWD in multivariate analysis (relative risk 0·26, 95 % CI 0·11, 0·61) in northern China, although no preventive effect of FA on AWD was observed in southern China. FA supplementation successfully reduced the prevalence of AWD in northern China.

Self-reported maternal cigarette smoke exposure during the periconceptional period and the risk for omphalocoele.

BACKGROUND: We investigated whether maternal exposure to cigarette smoke was associated with omphalocoele and whether periconceptional folic acid modified the association. METHODS: : We analysed data from the National Birth Defects Prevention Study on omphalocoele case (n = 301) and control (n = 8135) mothers for infants born from 1997 through 2007. Mothers who reported active smoking or exposure to second-hand smoke during the periconceptional period (1 month before conception to 3 months after) were considered exposed. Those who reported use of folic acid supplements during the same period were considered supplement users. Odds ratios and 95% confidence intervals were estimated using multivariable logistic regression adjusted for alcohol use, preconception body mass index, and race/ethnicity. RESULTS: One hundred fifteen (38.2%) case and 2592 (31.9%) control mothers reported exposure to cigarette smoke during the periconceptional period. Adjusted odds ratios [95% confidence intervals] were 1.19 [0.94, 1.53] for any smoke exposure, 0.87 [0.54, 1.40] for active smoking, 1.38 [1.00, 1.90] for second-hand smoke exposure, and 1.16 [0.80, 1.67] for both exposures combined. No dose-response relationship was observed. Folic acid-containing supplements did not reduce the risk for omphalocoele among women with active or second-hand smoke exposure. CONCLUSIONS: Self-reported active maternal smoking, with or without exposure to second-hand smoke, during the periconceptional period was not associated with omphalocoele. In contrast, there was a possible association with periconceptional exposure to second-hand smoke.

Occurrence of omphalocele in relation to maternal multivitamin use: a population-based study.

OBJECTIVE: We evaluated the association between mothers' use of multivitamin supplements and their infants' risk for omphalocele, a congenital anomaly of the abdominal wall. Omphalocele can occur in certain multiple congenital anomaly patterns with neural tube defects, for which a protective effect of multivitamins with folic acid has been demonstrated. METHODS: We used data from a population-based case-control study of infants born from 1968-1980 to mothers residing in metropolitan Atlanta. Case-infants with nonsyndromic omphalocele (n = 72) were actively ascertained from multiple sources. Control-infants (n = 3029), without birth defects, were selected from birth certificates by stratified random sampling. RESULTS: Compared with no use in the periconceptional period, periconceptional use of multivitamin supplements (regular use from 3 months before pregnancy through the first trimester of pregnancy) was associated with an odds ratio for nonsyndromic omphalocele of 0.4 (95% confidence interval [CI]: 0.2-1.0). For the subset comprising omphalocele alone or with selected midline defects (neural tube defects, hypospadias, and bladder/cloacal exstrophy), the odds ratio was 0.3 (95% CI: 0.1-0.9). These estimates were similar when the reference group also included women who began using multivitamins late in pregnancy (during the second or third month of pregnancy). The small number of participants limited the precision of subgroup analyses and translated into wide confidence intervals that included unity. CONCLUSIONS: Periconceptional multivitamin use was associated with a 60% reduction in the risk for nonsyndromic omphalocele. These findings await replication from additional studies to confirm the findings, generate more precise estimates, and detail possible mechanisms of actions.