Maternal circulating nutrient concentrations in pregnancy: implications for birth and placental weights of term infants.

BACKGROUND: Compromised fetal growth may program chronic diseases of adulthood, and it has been suggested that maternal nutrition is a major determinant of fetal growth. We previously found no clinically significant associations between maternal diet and the size of the infant and placenta at birth in a large cohort of white women living in the United Kingdom. OBJECTIVE: The objective was to examine the relations between indexes of maternal nutritional status in pregnancy and the birth and placental weights of infants born at term. DESIGN: We conducted a prospective cohort study of 798 white nulliparous women with singleton pregnancies. Blood samples were obtained at approximately 16 and 28 wk of gestation. RESULTS: The concentration of most nutrients was not associated with pregnancy outcome. High retinol and hemoglobin concentrations in late, but not in early, pregnancy were strongly and independently associated with lower birth weight and smaller placental size at birth. Each 0.1- micro mol increase in retinol predicted a 20.8-g (95% CI: 9.2, 32.5 g) decrease in birth weight (P < 0.001), and each 0.1-g/L increase in hemoglobin predicted a 61.5-g (95% CI: 28.5, 94.4 g) decrease in birth weight (P < 0.001). CONCLUSIONS: We found negative associations between birth and placental weights and maternal retinol and hemoglobin concentrations. These relations may be causal or may reflect an underlying metabolic dysfunction, such as failure of plasma volume expansion. Our results provide no evidence that having high circulating nutrient concentrations, for example, through the use of supplements, would improve infant and placental growth