Influence of maternal nutrition on outcome of pregnancy: prospective cohort study

Abstract Objective: To investigate the relations of maternal diet and smoking during pregnancy to placental and birth weights at term. Design: Prospective cohort study. Setting: District general hospital in the south of England. Participants: 693 pregnant nulliparous white women with singleton pregnancies who were selected from antenatal booking clinics with stratified random sampling. Main outcome measures: Birth and placental weights at term. Results: Placental and birth weights were unrelated to the intake of any macronutrient. Early in pregnancy, vitamin C was the only micronutrient independently associated with birth weight after adjustment for maternal height and smoking. Each ln mg increase in vitamin C was associated with a 50.8 g (95% confidence interval 4.6 g to 97.0 g) increase in birth weight. Vitamin C, vitamin E, and folate were each associated with placental weight after adjustment for maternal characteristics. In simultaneous regression, however, vitamin C was the only nutrient predictive of placental weight: each ln mg increase in vitamin C was associated with a 3.2% (0.4 to 6.1) rise in placental weight. No nutrient late in pregnancy was associated with either placental or birth weight. Conclusions: Concern over the impact of maternal nutrition on the health of the infant has been premature Maternal nutrition, at least in industrialised populations, seems to have only a small effect on placental and birth weights. Other possible determinants of fetal and placental growth should be investigated. Key messages Placental and infant birth weights were not associated with the intake of any macronutrient early or later in pregnancy After adjustment for the effects of maternal height and smoking, only vitamin C independently predicted birth weight. The expected mean difference in birth weight for infants with mothers in the upper and lower thirds of intake was about 70 g Vitamin C was the only nutrient that independently predicted placental weight, but again this relation was of doubtful clinical significance Among relatively well nourished women in industrialised countries, maternal nutrition seems to have only a marginal impact on infant and placental size. Other causes of variation in the size of clinically normal infants should now be investigated