This is according to a new randomised controlled trial involving 274 participants, aged 21 to 45 years with a pre-pregnancy BMI of ≥25 kg/m2 and within 16 weeks of gestation.
In the control group (n = 137), participants received standard prenatal multivitamin supplement tablets, specifically "Obimin," containing 400 IU of vitamin D3, along with folic acid, vitamin B1, B2, B6, B12, and other minerals.
Meanwhile, participants in the intervention group (n = 137) received an additional oral-dissolving vitamin-D3-only supplement, contributing an extra 400 IU, in conjunction with Obimin.
All participants underwent baseline investigations during the antenatal visit between 10- and 16-weeks gestation. Follow-up assessments on diet and lifestyle were conducted by research staff at 24–28 weeks gestation through questionnaire administration.
Post-delivery, data on obstetric complications, delivery, and birth outcomes were extracted from hospital case notes.
Researchers note that at 24–28 weeks gestation, the intervention group exhibited a notably higher level of plasma 25-hydroxyvitamin D (25OHD) at 61.45 nmol/L (SD 16.74) compared to the control group at 53.46 nmol/L (SD 16.20).
The increase in 25OHD from baseline to 24–28 weeks gestation was more pronounced in the intervention group, showing a rise of 21.52 nmol/L, as opposed to the control group's increase of 14.52 nmol/L.
Furthermore, a greater proportion of participants in the intervention group (n = 87, 77.7%) achieved sufficient vitamin D levels with 25OHD ≥ 50 nmol/L, surpassing the control group (n = 66, 55.5%).
Regarding birth outcomes, infants born to women with obesity who received the intervention exhibited a lower incidence of low birth weight (3.9% vs. 17.0%, p = 0.032) and a greater birth length (49.06 cm vs. 48.06 cm, p = 0.024) compared to those born to women with obesity in the control group.
Significance of increased vitamin D supplementation
Despite the absence of seasonal variation in UV exposure in Singapore, a country unlike many others, researchers posit that the administration of 800 IU/day of vitamin D3 effectively boosts 25OHD levels and enhances vitamin D sufficiency among overweight/obese pregnant women.
They acknowledge conflicting findings in existing literature concerning the effects of vitamin D supplementation during pregnancy; an uncertainty that is particularly pronounced for pregnant women grappling with overweight and obesity. This demographic, susceptible to pregnancy complications and more prone to vitamin D insufficiency due to the sequestration of this fat-soluble vitamin within adipocyte lipid droplets, may experience seizures and dilated cardiomyopathy due to hypocalcaemia. Moreover, it is associated with an increased incidence of acute lower respiratory tract infections and recurrent wheezing in the first five years of a child's life.
In Singapore, the prevailing standard of care involves supplementing pregnant women with 400 IU/day of vitamin D through antenatal multivitamins. Notably, approximately one-third of women in Singapore contend with overweight/obesity (body mass index (BMI) ≥ 25 kg/m2) during pregnancy.
Consequently, researchers advocate for larger trials encompassing varying higher doses of vitamin D3 supplements and increased sample sizes to comprehensively assess their impact on maternal and birth outcomes within this population.
“800 IU/day of vitamin D3 supplementation effectively increased the 25OHD levels and improved the vitamin D sufficiency status in pregnant women with OW/OB in pregnancy…” Researchers wrote.
“In subsequent studies, it would be valuable to delve deeper into the effects of vitamin D3 supplementation on long-term maternal and foetal outcomes beyond delivery timepoint.”
The Effect of Vitamin D Supplementation in Pregnant Women with Overweight and Obesity: A Randomised Controlled Trial
Authors: Chee Wai Ku et al.