The study published in American Journal of Clinical Nutrition checked the amounts of choline and iodine in over-the-counter and prescription prenatal vitamins. The research also controlled for toxic metals such as arsenic, lead and cadmium.

“During pregnancy, many women depend on prenatal vitamins and minerals to support their health and their baby’s development. Among the most critical nutrients for fetal development are choline and iodine. Some prenatal vitamins may not contain the exact amounts listed on the label and some may not contain any choline or iodine,” said study first author Laura Borgelt, PharmD, MBA, professor at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences at CU Anschutz. “Our study aims to help women better understand the nutritional content of prenatal supplements, empower them to make more informed choices and choose the best options for their health and the well-being of their baby.”

The researchers tested a selection of 47 different prenatal vitamins (32 over-the-counter and 15 prescription products) purchased from online and local stores where people typically shop. They then measured the actual amounts of choline and iodine in their lab compared to what was on the label and also checked for arsenic, lead and cadmium. They compared their results with official safety standards within 20% of the claimed amount.

The Food and Nutrition Board of the Institute of Medicine recommends dietary reference intakes for choline at 450 mg/day during pregnancy and 550 mg/day during lactation, with a tolerable upper limit of 3,500 mg/day. For iodine, the recommended dietary reference intake for women 19 years and older is 150 mcg/day, increasing to 220 mcg/day during pregnancy and 290 mcg/day during lactation. The tolerable upper limit for iodine is 1,100 mcg/day.

In addition, the United States Pharmacopeia has established drug purity standards, including limits for harmful substances: arsenic (2.5 mcg per oral daily dose), cadmium (0.5 mcg per oral daily dose), and lead (0.5 mcg per oral daily dose ).

The researchers found that most prenatal vitamins do not contain choline, and many of those that do do not contain the correct amount. Only 12 stated the choline content, which is about 26% and only five products (42%) had the correct amount of choline as promised on the label.

When they checked for iodine, they found that most prenatal vitamins contain less than advertised, and very few provided the correct amount, with 53% of products containing iodine, but only four (16%) products containing the claimed amount of iodine on the label.

They also found that some products contained levels of heavy metals that were higher than expected. Seven products had too much arsenic, two had too much lead and 13 had too much cadmium, all above purity limits set by the US Pharmacopoeia. Exposure to these heavy metals during pregnancy has been associated with adverse birth outcomes.

“We are one of the first studies to measure the actual amounts of choline and iodine in a large sample of prenatal supplements. The presence of contaminants, particularly cadmium, was also of concern. Our results show a significant gap between what is on the labels and what that are actually in the products, which underlines the urgent need for stronger regulatory oversight in this area,” adds Borgelt.

The authors mention that while there is a need for more oversight to ensure that supplements have enough of each ingredient, it is still important to take supplements during pregnancy. They recommend double-checking ingredients or working with a doctor or healthcare professional to choose the prenatal supplement.

This study was funded by the Center for Science in the Public Interest through a grant from the John Sperling Foundation.