During pregnancy maternal nutritional deficiencies can negatively impact the development and function of the placenta, which acts as the interface between the mother and fetus.  Placental complications can lead to poor pregnancy outcomes in the mother (such pre-eclampsia) and in the baby (such as low birthweight, preterm birth and stillbirths). Providing pregnant women with nutritional supplements or other dietary interventions, such as counselling women on their diet might prevent the poor pregnancy outcomes. We performed an umbrella review of the results of earlier systematic reviews on nutritional supplements in pregnancy.  We found 91 meta-analyses covering 23 types of nutrient supplements and three types of dietary interventions for pregnant women. We found that vitamin D supplementation together with calcium or each on their own, and multiple micronutrients had a moderate beneficial effect on preventing pre-eclampsia. Vitamin D supplements also had a moderate beneficial effect on preventing infants who were small for gestational age. Moderate beneficial effects were also found with calcium on preventing preterm birth and balanced protein-energy supplementation on prevention of stillbirths. However no interventions were shown to reduce rates of maternal death. Other interventions resulted in weak, not discernible or not significant associations on pregnancy outcomes. Although this umbrella review covers an impressive body of global research spanning decades, these findings are limited by poor quality of evidence and areas where the evidence was sparse, and knowledge is lacking.  We suggest that more research is needed to examine the relationships between supplementation and underlying maternal nutritional deficiencies, which has been reported as common in low- and middle-income settings. Research with pregnant mothers in sub-Saharan Africa on maternal diets and nutrient supplement usage in association with placental complications within the PRECISE Network has the potential to help fill in some of these knowledge gaps.

“We are very excited about our umbrella review, which compiles together over five decades of maternal nutritional supplementation and dietary intervention trials from all around the world. It shows that there are topics with well-established evidence but also emerging areas as well. We still have so much to learn!” – Maggie Woo Kinshella.

Kinshella, M.-L.W.; Omar, S.; Scherbinsky, K.; Vidler, M.; Magee, L.A.; von Dadelszen, P.; Moore, S.E.; Elango, R.; The PRECISE Conceptual Framework Working Group. Effects of Maternal Nutritional Supplements and Dietary Interventions on Placental Complications: An Umbrella Review, Meta-Analysis and Evidence Map. Nutrients 2021, 13, 472.