The association of maternal diet and dietary supplement intake in pregnant New Zealand women with infant birthweight

Objective: To investigate the association of infant birthweight with maternal diet and supplement intake. Subjects/Methods: Prospective cohort study of 504 European and Polynesian urban and rural pregnant volunteers recruited from northern New Zealand clinics. Subjects were visited in months 4 (mth4) and 7 (mth7) of pregnancy when height, weight and skinfolds were measured, questionnaires to determine personal details administered, and diet assessed by a 24-hour recall and 3-day food record. Results: After adjusting for confounders nutrients accounted for up to 5.0% of the total variance in birthweight. Ethnicity was not a significant confounder. A quadratic relationship existed between birthweight and % total energy (%TE) from carbohydrate, fat and protein, most significantly with carbohydrate energy (P = 0.002). Birthweight was greatest (similar to 3600 g) when carbohydrate %TE was 48%, fat 35% and protein 17%. Birthweight was reduced with high beta-carotene intakes (mth4, P = 0.009) and with both high retinol and b-carotene intakes in mth4 and 7 (average). Birthweight was positively associated with increasing pantothenic acid/biotin ratios (P = 0.011), magnesium (P = 0.000) and vitamin D (P = 0.015) intakes in mth4; with biotin (P = 0.040) and B-12 intakes above the RDI (P = 0.006) in mth7; and with pantothenic acid intake in mth4&7 ( P 0.002). Dietary supplement usage was associated with increased birthweight, most significantly iron supplementation (P = 0.006). Conclusion: Birthweight was associated with the % TE from carbohydrate, fat and protein, and with b-carotene, retinol, vitamins D and B-12, pantothenic acid, biotin and magnesium intakes and iron supplementation. More research may be required on some dietary recommendations for pregnancy. European Journal of Clinical Nutrition (2010) 64, 184-193; doi: 10.1038/ejcn.2009.134; published online 18 November 2009