In the last years evidence has shown how lifelong well-b eingstrongly depends on intrauterine growth and development during intrauterine life. Fetal growth can achieve its full potential only with an adequate and fine-tuned interaction between mother, placenta and fetus. Several environmental and maternal factors like maternal diet, body composition and endocrine status may alter this delicate equilibrium. Moreover, placental function and metabolism contribute and regulate the availability of fetal nutrients. Changes in this complex mechanism may compromise the pregnancy outcome. In this chapter we wish to elucidate the physiologic mechanisms that regulate this interaction and how also little modifications may predispose to pathologies like intrauterine growth restriction and gestational diabetes with important consequences on fetal and adult health.
Gestational weight gain is a strong predictor of short- and long-term health outcomes for both childbearing women and their offspring. Epidemiologic studies have found that higher maternal gestational weight gains are associated with abnormalities in maternal prenatal glycemia, hypertensive disorders of pregnancy and delivery complications, along with an increased risk of postpartum weight retention, incident obesity and adverse cardiometabolic sequelae in mothers by midlife. Additionally, observational data have linked greater gestational weight gains to increased fetal growth and later childhood obesity. Associations of gestational weight gain with preterm birth and infant mortality may be U-shaped, such that the risks are increased with both low and high gains. In an attempt to optimize both maternal and child outcomes, the Institute of Medicine revised gestational weight gain guidelines in 2009, recommending smaller gains for women with higher prepregnancy body mass indices, particularly for women entering pregnancy with a body mass index of at least 30. However, it is as of yet unclear if these new recommendations will lead to improvements in the proportions of women gaining recommended amounts, and in maternal and child health. As fewer than one third of mothers currently gain within the ranges recommended by the Institute of Medicine, interventions to help mothers achieve healthy gestational weight gains are of critical public health importance.
This review summarizes current knowledge on the effectiveness of prenatal nutrient supplements ranging from iron-folic-acid (IFA), which is standard of care in many parts of the world, to more novel ones such as w–3 fatty acids and probiotics in improving maternal and child health outcomes. Randomized controlled trials have shown that prenatal IFA supplements reduce the risk of anemia and iron deficiency during pregnancy and at term, but the evidence of risk reductions in low birth weight (LBW) and preterm delivery (PTD) is weak. Recent studies, however, suggest that prenatal IFA supplements may reduce child mortality. On the other hand, there is convincing evidence that multiple micronutrient supplements containing 1–2 recommended daily allowances of several vitamins and minerals are safe and reduce the risk of LBW by 19 and 17% when compared to a placebo or routine IFA. Prenatal calcium supplements ( 1 1 g/day) have also been shown to significantly reduce the risk of preeclampsia and maternal death or serious morbidity by 52 and 20%, respectively. Zinc and fish oil supplements containing w–3 fatty acids may also increase gestational age and reduce the risk of PTD, but not of LBW, in selected populations. There is, however, limited evidence to support the provision of supplements containing only vitamin A, D or antioxidants such as vitamins C and E. Although the protective effect of folic acid during the periconceptual period in reducing neural tube defects is well established, very few or no intervention trials have evaluated the independent effects of specific B vitamins (vitamins B 6 , B 12 and folic acid), docosahexanoic acid and probiotics during pregnancy. The effects of prenatal iodine supplements in areas with mild to moderate iodine deficiency have not been examined either. Some of these nutrients may not affect outcomes such as PTD or LBW but may have long-term benefits for offspring health and development.