Endocrine Abstracts

Background: The importance of vitamin D supplementation in pregnancy is well known. Hypovitaminosis D is associated with adverse maternal and foetal outcomes such as pre-eclampsia, gestational diabetes mellitus, bacterial vaginosis, increased incidence of caesarean section delivery, intra-uterine growth restriction and reduced bone and muscle mass in childhood. The recommendations for vitamin D supplementation vary widely, with NICE guidelines suggesting a daily replacement dose of 400 IU/day. The aim of this study was to determine whether the recommended replacement dose of cholecalciferol of 400 IU/day was sufficient to maintain normal vitamin D level (25(OH)D >50 nmol/l) in pregnant patients.

Methods: Serum 25-hydroxyvitamin D (25(OH)D) levels of 129 pregnant women who attended the joint antenatal and diabetes clinic between 17/02/21 to 27/04/21 were analysed. All the patients were on standard vitamin D supplement of 400 IU/day (pregnacare) from the time of antenatal booking. Blood was collected for 25(OH)Dat the time of oral glucose tolerance test at 26-28 weeks of gestation.

Results: The mean 25(OH)D level was noted to be suboptimal across the study population (47.92 nmol/l), with the mean in South Asians (43.99 nmol/l, n=37) lower than their Caucasian counterparts (49.50 nmol/l, n=92) (P=0.0487). Low 25(OH)D level (<50 nmol/l) was observed in 58.91% of the patients, more prevalent in South Asians (67.57%), compared to Caucasians(55.43%). Significantly reduced 25(OH)D (<30 nmol/l) was noted in 15.5% of the patients, also more prevalent among South Asians (21.62%) compared with Caucasians (13.04%).

Conclusion: Our study suggested that vitamin D supplementation of 400 IU/day in pregnant women resulted in suboptimal 25(OH)D levels, more pronounced in South Asians compared to Caucasians. The results suggest the need to revise the guidelines for higher dose of vitamin D supplementation during pregnancy. Larger studies are required to validate the findings.