Exogenous Factors and Female Reproductive Health

Undernutrition adversely affects fertility. A low body weight is associated with delayed conception. When conception does occur, undernutrition could also adversely affect pregnancy outcomes. Low prepregnancy BMI (<18.5 kg/m2) is associated with increased risk of early miscarriage, preterm labour, anaemia, insufficient weight gain, and impaired intrauterine fetal growth. On the other hand, overweight and obesity are associated with increased risk of gestational diabetes, pre-eclampsia, and other complications during pregnancy and delivery. Weight loss through energy restriction, with or without exercise, improves reproductive function in overweight or obese women. Aside from body weight and energy status, maternal macronutrient, and micronutrient intakes before and during pregnancy would also influence pregnancy outcomes. Studies in mostly nutritionally at-risk women reported that balanced energy/protein supplementation (<25% energy from protein) is associated with higher birth weights but high protein supplementation (> 25% energy from protein) may increase the risk of small-for-gestational-age (SGA) infants. Reducing glycaemic index or glycaemic load of maternal diet may reduce the risk of large-for-gestational-age (LGA) births or gestational diabetes. In terms of micronutrients, current evidence supports folic acid supplementation (at least 400 µg/day) to reduce the risk of fetal abnormalities, iodine supplementation for women at risk of iodine deficiency to prevent complications in fetal physical and mental development, and iron supplementation to reduce the risk of maternal anaemia where required.