1. Introduction
COMPLICATIONS
These authors contributed equally to this work.The impact of vitamin D supplementation on 25-hydroxyvitamin D (25OHD) levels, metabolic status, and pregnancy outcomes in pregnant women with overweight and obesity (OW/OB) is uncertain. This study aimed to examine whether administrating 800 IU of vitamin D3 orally would improve maternal serum 25OHD levels, lipid profile, and pregnancy outcomes compared to 400 IU. This was a two-arm, parallel, non-blinded randomised controlled trial involving 274 pregnant women recruited from KK Women’s and Children’s Hospital, with a body mass index of ≥25 kg/mVitamin D, an essential nutrient, is primarily produced through the conversion of 7-dehydrocholesterol in the skin upon exposure to ultraviolet B radiation. Aside from its well-established role in calcium homeostasis, vitamin D regulates numerous cellular processes [However, the existing literature revealed conflicting results regarding the impact of vitamin D supplementation during pregnancy. While some studies suggest that antenatal vitamin D supplementation can improve serum 25OHD levels and reduce the risks of the aforementioned complications [Nearly one-third of women in Singapore are affected by OW/OB (body mass index (BMI) ≥ 25 kg/m