Even though prenatal vitamins are widely recommended to pregnant women to help meet the nutrient needs for mothers and babies, women may struggle to choose the right supplement because labelling is inconsistent and the amount of the active ingredients varies widely from one product to the next, researchers note in the Journal of the Academy of Nutrition and Dietetics.
There’s no single right choice, experts say.
Pregnant women should discuss their diet with their doctor before choosing a supplement, and try as much as possible to get needed nutrients from the foods they eat during pregnancy, said Deborah O’Connor, a nutrition researcher at the University of Toronto who wasn’t involved in the new research.
For the study, investigators examined labelling for 82 prescription and 132 nonprescription products in the US They looked for doses of seven vitamins and minerals, non-nutrient ingredients, and safety information.
Overall, prescription products had higher amounts of folic acid, which helps prevent brain and spinal cord birth defects, the study found.
Prescription supplements typically had fewer vitamins – 9 compared with 11 for nonprescription options – and fewer minerals – 4 compared with 8 for nonprescription products.
“They can vary substantially in their nutrient content,” said lead study author Dr Leila Saldanha, of the Office of Dietary Supplements at the National Institutes of Health.
“Generally, most provide the amounts of nutrients that are recommended during pregnancy,” Saldanha said by e-mail.“Overall, however, prescription prenatals are less potent than nonprescription prenatals, except for folic acid.”
Both types of supplements had similar amounts of zinc, iron and docosahexaenoic acid (DHA), an omega-3 fatty acid in fish oil that can support healthy development of a baby’s brain, nervous system and eyes, the study also found.
All of the vitamins had higher than the recommended dose of at least one nutrient, based on US dietary guidelines for pregnant and lactating women.
About 33% of the nonprescription products contained botanical ingredients, compared with 6 % of prescription prenatals.
Nonprescription products were also more likely to contain probiotics, although only 8 % did, compared with 2 % of prescription alternatives.
Only prescription products contained the stool softener docusate sodium.
One limitation of the study is that researchers looked just at the declared amount on labels, and not at data on the actual amounts found in analysis of the supplements, the authors note.
For some women, insurance benefits and costs may influence what supplement they choose, because prescription products may come with lower out-of-pocket costs, O’Connor pointed out in an e-mail.
Whatever they choose, women should try to avoid taking supplements that contain doses of vitamins and minerals that are higher than the recommended maximum amounts for pregnant women, she said.
Also, she advises, women should consume a varied diet higher in vegetables, fruit, whole grains, low- or non-fat dairy, seafood, legumes and nuts, “and I would suggest that they lower their intake of red and processed meats and limit sugar-sweetened beverages and refined grains.”
When they follow this advice, they may still need supplements, though.
“Even if their diet is a healthy one, I still recommend, as do most professional organisations, that women planning a pregnancy consume a 400ug folic acid containing multivitamin supplement,” O’Connor said.
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