Birth outcomes relative to dietary vitamin D & calcium intake in obese pregnant women

Abstract

For individuals with limited exposure to ultra-violet B, a recommended nutrient intake (RNI) of 10 mug/day of vitamin D is recommended; this includes all pregnant and lactating women(1). Despite this, research suggests a subset of pregnant women are at risk of vitamin D insufficiency due to obesity, darker skin pigmentation and estimated delivery date in spring or summer(2). There is no increase in requirements for calcium during pregnancy however a positive maternal calcium balance is dependent on adequate circulating levels of 25(OH)D3 (3). Maternal outcomes such as gestational diabetes, pre-eclampsia and increased risk of caesarean section are all associated with low vitamin D status(4). The aim of this study was to investigate whether dietary intakes of vitamin D and calcium were associated with adverse maternal and birth outcomes. Participants were asked to complete three-day food diaries during each trimester of pregnancy. Data regarding food portion size was verified using a food atlas(5) and the diaries were then analysed using MicrodietTM. Data were collected for 140 women with a BMI > 35 kg/m2 (n = 139), a mean booking-in weight of 110kg (SD 15.5) and mean birth weight of 3.57 kg (SD 0.67). Most women achieved total energy requirements at all 3 visits however there was a wide distribution around the mean with an average minimum intake of 706 kcals for all 3 visits and a maximum intake of 3906 kcals. There was a positive dietary intake for calcium with 73.6% of women achieving RNI and 95.7% achieving LRNI. Dietary intake of vitamin D was low with only 2.2% of women achieving RNI at all 3 visits. Spearman's correlation suggests an association with vitamin D and birth weight (rho = 0.224, p = 0.036) at visit 1. This suggests that vitamin D status in early pregnancy may influence birth weight and that pre-natal supplements may be necessary. Results indicate that further investigation into the quality of maternal diet and pregnancy outcomes is required.