Vitamin D for pregnant women should be tailor-made

Vitamin D is a hormone that helps the body absorb calcium. It plays a crucial role in bone and muscle health. 

The skin naturally produces vitamin D after exposure to sunlight but people also obtain smaller amounts of the vitamin through foods, such as milk fortified with vitamin D.

The findings showed that women who delivered in the summer season, who gained less weight during pregnancy and who had higher vitamin D levels early in pregnancy tended to have higher levels of vitamin D in the blood than their counterparts. 

On the other hand, vitamin D supplements were found less effective at raising the levels of the vitamin in pregnant women who delivered their babies in the winter season, have low levels of vitamin D early in pregnancy or gain more weight during pregnancy.

Women who consistently took the supplement also had higher levels of vitamin D than participants who did not, the researchers said.

"Our study findings suggest that in order to optimise vitamin D concentrations through pregnancy, the supplemental dose given may need to be tailored to a woman's individual circumstances, such as the anticipated season of delivery," said Nicholas Harvey, Professor at University of Southampton in Britain. 

Evidence suggests vitamin D deficiency during pregnancy can harm maternal health, foetal development and the child's long-term skeletal health.

"It is important for pregnant women to have sufficient levels of vitamin D for the health of their baby," Harvey added. 

For the study, the team recruited and randomised more than 800 pregnant women to take either 1,000 units (25 micrograms) of vitamin D every day or a matched placebo capsule from 14 week's gestation until delivery of the baby.

Analysis showed that participants who received the vitamin D supplement achieved different levels of vitamin D in the blood, even though they received the same dose. 

The study was published in the Journal of Clinical Endocrinology & Metabolism.