In contrast , we did not find any beneficial effect of  folate supplementation on placental weight or on length of gestation .
There is a paucity of well-conducted RCTs investigating the effect of  folate supplementation on health outcomes in pregnancy .
The beneficial effect of folic acid supplementation before and shortly after conception is well recognized , whereas the effect of supplementation during the second and third trimesters is controversial and poorly documented .
Our aims were to systematic ally review r and omized controlled trials ( RCTs ) investigating the effect of folate supplementation on birth weight , placental weight and length of gestation and to assess the dose – response relationship between folate intake ( folic acid plus dietary folate ) and health outcomes .
Maternal periconceptional use of multivitamins and reduced risk for conotruncal heart defects and limb deficiencies among offspring.
We investigated whether a woman 's periconceptional use of a multivitamin containing folic acid was associated with a reduced risk for delivering offspring with a conotruncal heart defect or a limb deficiency .  Data were derived from a population -based case-control study of fetuses and liveborn infants with conotruncal or limb defects among a 1987 - 88 cohort of births in California .  Telephone interviews were conducted with mothers of 207 ( 87.0 % of eligible ) conotruncal cases , 178 ( 82.0 % ) limb defect cases , and of 481 ( 76.2 % ) r and omly selected liveborn nonmalformed control infants . Reduced risks were observed for maternal use of multivitamins containing folic acid from one month before until two months after conception . Odds ratios and 95 % confidence intervals for any compared to no multivitamin use were 0.70 ( 0.46 - 1.1 ) for conotruncal defects and 0.64 ( 0.41 - 1.0 ) for limb defects . Controlling for maternal race/ethnicity , age , education , gravidity , alcohol use , and cigarette use result ed in a further reduction to the odds ratio for conotruncal defects , 0.53 ( 0.34 - 0.85 ) , but not for limb defects . Among non-vitamin using women , consumption of cereal containing folic acid was also associated with reduced risk for both defects . Women who take multivitamins have 30 - 35 % lower risk of delivering offspring with either conotruncal or limb defects . This association may not be attributable to folic acid specifically , but may be a consequence of other multivitamin components , or some unknown behaviors that highly correlate with regular use of a multivitamin . However , should the association prove causal , it offers an important opportunity for preventing thous and s of serious birth defects
In contrast , we did not find any beneficial effect of  folate supplementation on placental weight or on length of gestation .
There is a paucity of well-conducted RCTs investigating the effect of  folate supplementation on health outcomes in pregnancy .
The beneficial effect of folic acid supplementation before and shortly after conception is well recognized , whereas the effect of supplementation during the second and third trimesters is controversial and poorly documented .
Our aims were to systematic ally review r and omized controlled trials ( RCTs ) investigating the effect of folate supplementation on birth weight , placental weight and length of gestation and to assess the dose – response relationship between folate intake ( folic acid plus dietary folate ) and health outcomes .