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 .
[Deficiency of folates in pregnancy: effect of supplementary folic acid].
Higher folate needs are present during pregnancy , which may lead to tissular deficiency in the mother and to depleted newborn folate reserves . The aim of this work was to assess the prevalence of folate deficiency and to establish the rates of serum and red cell folate in two groups of mothers and newborn infants , one receiving only iron and the other iron and folate during pregnancy .  The rates of serum and red cell folate found at the end of pregnancy were significantly higher in the group which received folate ; however , the percentage of cases with tissular folate deficiency was low in both groups , with no significant difference ( 3.8 % and 1.3 % , respectively ) . These findings , along with the lack of effect of supplemental folate on erythropoiesis , pose some questions on the usefulness of supplemental folate during pregnancy in our country
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 .