Prenatal multivitamins are an "unnecessary expense" according to a review published by BMJ earlier this week, which advised pregnant women to focus on supplementing with folic acid and vitamin D supplements while improving their overall diet. According to BMJ, prenatal supplements oftentimes contain more than 20 vitamins and minerals, such as vitamins B1, B2, B3, B6, B12, C, D, E, K, folic acid, iodine, magnesium, iron, copper, zinc and selenium, at a cost of almost $20 per month.

BMJ advocated supplementation of folic acid and vitamin D, but nothing else. They may have misssed supplements crucial to healthy fetal development, such as iodine and iron, argued an American trade association representing the dietary supplement industry.

"Reputable medical organizations, including the American Academy of Pediatrics, the Endocrine Society and the American Thyroid Association, recommend that pregnant women take a multivitamin as a way to assure they are getting adequate nutrients such as folic acid and iodine that are critical for the development and well-being of the fetus, as well as for their own health," countered Duffy MacKay, SVP scientific and regulatory affairs for the Council for Responsible Nutrition, a U.S. association representing the dietary supplement industry. "In fact, iodine is now recognized as a nutrient so critical to the cognitive development of the baby during pregnancy that CRN recently developed guidelines urging the dietary supplement industry to ensure that prenatal multivitamins contain at least 150 mcg of iodine daily," he said.

BMJ's arguments against supplementing a diet with a multivitamin may be misguided, CRN argued.

"It is unfortunate that, in addition to disregarding the immense value a multivitamin and its ingredients can provide pregnant women, the authors fail to acknowledge that conducting randomized controlled trials on a multivitamin in pregnant women would be unethical as you cannot deprive a pregnant woman of essential nutrients," noted MacKay. "When the totality of all available evidence is considered, the value of nutrient supplementation during pregnancy makes a clear case."