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 .
The relationship between maternal dietary intake and infant birthweight.
BACKGROUND Zinc and folate are important for fetal growth . However , the relationship between the dietary intake of these nutrients and pregnancy outcome is not settled . METHODS A prospect i ve study was conducted to ascertain the relationship between  maternal dietary zinc and folate intake  ( n = 1398 ) , serum zinc and folate levels ( n = 289 ) , and infant birthweight .  Twenty-four hour recalls were used to measure energy , zinc , folate and other nutrient intakes at 18 and 30 weeks of gestation . Subjects in the study were offered daily folic acid ( 1.0 mg ) and iron ( 60 mg as ferrous sulfate ) at enrollment . RESULTS Maternal zinc nutriture as assessed by serum and dietary intake was not associated with birthweight or length of gestation . There was a small but significant positive association between maternal folate intake and adjusted infant birthweight ( beta = 0.05 , p = 0.03 ) . The indirect measures of maternal nutritional status including maternal pre-pregnancy weight ( beta = 8.0 , p = 0.0001 ) and weight gain during pregnancy ( beta = 18.1 , p = 0.0001 ) were stronger predictors of adjusted infant birthweight as compared to energy intake and intake of zinc and folate . An increase of 320 , 290 , and 48 g in infant birthweight was associated with the 90th-10th percentile difference for pre-pregnancy weight , weight gain during pregnancy , and folate intake respectively . CONCLUSION These results indicate that pre-pregnancy weight and weight gain during pregnancy are both strong predictors of infant birthweight .  Folate intake , although significantly associated with birthweight , was a weak predictor while maternal intake of zinc and other nutrients was not associated with birthweight
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 .