| This prospective study explored the maternal serum level of 25(OH)D in Chinese pregnant women in Hong Kong and the factors affecting 25(OH)D level. It also explored the correlation between maternal 25(OH)D with PTH level, maternal musculoskeletal complaints, adverse pregnancy outcome, maternal bone turnover during pregnancy and postpartum, and the bone development of the offspring, aiming to explore and establish a normal range of 25(OH)D level in pregnancy for the Hong Kong Chinese women.;A total of 237 women with singleton pregnancy and 62 women with multiple pregnancies were recruited for the cohort study from August, 2010 to November, 2011. Maternal blood samplings for 25(OH)D and PTH measurements were performed at recruitment, 24-28 weeks, 31-36 weeks of gestation, and 6-11 weeks postpartum respectively. A questionnaire which included the monthly dietary and supplement intake of vitamin D, questions about sunlight exposure, and musculoskeletal complaints was administered on each visit. A 75g oral glucose tolerance test (OGTT) was performed on cohort cases at 24-28 weeks of gestation. Measurements of the speed of sound (SoS) at the distal one third of the maternal radius and the proximal phalanx of the third finger of the non-dominant side were performed with quantitative ultrasonography (QUS) measurement during the visits at the first and third trimesters, and postnatal period. The SoS at the left mid-shaft tibia of the offspring was determined during the postnatal visit. Maternal characteristics, ultraviolet radiation (UVR) intensity at blood sampling, and pregnancy outcome, were also recorded. Cases with pregnancy complications were recruited for case-control studies, and maternal 25(OH)D level was examined with respect to preterm birth (PTB), preeclampsia (PET), gestational diabetes (GDM), and fetal growth restriction (FGR, birthweight below the 10th percentile of the customized estimated birthweight). The controls were matched for booking body mass index (BMI) and UVR intensity at blood sampling.;The mean 25(OH)D level in ranged from 44.7 +/- 12.6 to 48.9 +/- 17.1 nmol/l in the three trimesters, and was related to BMI, vitamin D supplementation, UVR intensity at blood sampling, and the acceptance of sunlight exposure, but not the number of fetus, parity, gestational age, or the completion of pregnancy.;Inverse correlation between PTH and 25(OH)D were observed in singleton, but not in multiple, pregnancy. The change in maternal PTH level is found to be relatively independent from that of 25(OH)D. There was no correlation between maternal 25(OH)D level with musculoskeletal complaints, postnatal recovery, bone turnover during and after pregnancy, or the bone density of the offspring. Maternal 25(OH)D level was lower in women with early PTB (< 34 weeks), PET, and FGR, but not for GDM. A maternal 25(OH)D level of lower than 34.3nmol/l and 50 nmol/l was associated with increased risk of early PTB, PET, and FGR respectively. But the correlation between maternal 25(OH)D level with FGR might be affected by supplementation.;In conclusion, serum level of 25(OH)D is insufficient in reflecting maternal vitamin D status and metabolism in pregnancy, and is of limited use in predicting adverse pregnancy outcome. |
