By Joene Hendry
Pregnant women involved in a Canadian study designed to assess the tolerability of different prenatal vitamin formulations, took only about half the vitamins recommended, researchers report.
"This strongly suggests that women in the general population who are not encouraged to take vitamins, comply even less," Dr. Gideon Koren told Reuters Health.
Moreover, the iron content of the vitamins does not appear to be a factor in low adherence rates, as had been supposed, Koren, at the Hospital for Sick Children, in Toronto, Ontario, and colleagues found.
It is important for babies' wellbeing to find out how to help the many women with early pregnancy morning sickness who find it difficult to take prenatal vitamins, said Koren. His team previously found that tablet size played a role in prenatal vitamin adherence.
Their current study, published in BioMed Central's journal Pregnancy and Childbirth, assessed whether the amount of iron, a potential morning sickness aggravator, also plays a role in prenatal vitamin adherence among otherwise healthy pregnant women in their first 20 weeks of gestation.
The investigators randomly assigned 92 women to take a prenatal multivitamin containing 35 milligrams of elemental iron (low iron) and 75 women to a multivitamin containing 60 milligrams of iron (high iron) through the remainder of their pregnancy.
The study participants had contacted the hospital's counselling program to obtain information on the safety or risk related to prenatal vitamin use or discontinuation. Most had stopped taking a previous multivitamin supplement due to nausea and vomiting, the investigators note.
Based on monthly interviews, 38 percent of the women took at least 80 percent of their pills, which was considered adherent, and the average pill intake was only about 50 percent. The investigators found no difference in adherence between women taking low iron and high iron vitamins.
These findings, combined with the group's previous research, indicate that tablet size may be a more important factor than iron content affecting prenatal vitamin use.
Koren's group concludes that unless prenatal multivitamin formulations change, adherence may not improve significantly above 50 percent.