NEW YORK (Reuters Heath) – Expectant moms who get a lot of iron in their first trimester tend to have heavier, although still healthy-weight, babies, English researchers say. They did not find the opposite trend – that insufficient iron intake in early pregnancy led to lower birthweights, however.
Specifically, the more daily iron women got from food or supplements, the bigger their babies, according to the report published in the journal Human Reproduction.
U.S. guidelines recommend that pregnant women get 27 milligrams of iron a day. In the U.K., all women are urged to get at least 15 milligrams a day.
That 15 milligrams equals about three pounds of roasted chicken breast, 15 cups of raw spinach, or a half-cup of iron-fortified breakfast cereal. Most prenatal vitamins contain at least 18 milligrams of iron, and cost between $3 and $40 a month.
“Iron intake affects body iron stores, which are under extra demand during pregnancy,” said study co-author Nisreen Alwan, research fellow at the University of Leeds School of Food Science and Nutrition.
The majority of pregnant women in the U.K. aren’t meeting even the general iron intake recommendation, Alwan said in an e-mail. Most get about 11.8 milligrams of iron per day from both food and supplements.
The researchers surveyed about 1,260 women on what they ate and whether they took iron supplements during all three trimesters of their pregnancies.
They found that for every 10 milligrams per day increase in total iron intake, there was around a 34 gram (1.19 ounce) increase in their babies’ birthweights.
The low cutoff for a normal-birthweight baby is 2,500 grams (five and a half pounds). The average baby in the study weighed about 3,400 grams (around seven and half pounds), and only about one in 25 babies fell into the low-birthweight category.
“It was actually a very small effect that they picked up,” said Laura Caulfield, professor at The Johns Hopkins University Bloomberg School of Public Health, who was not involved in the study.
The researchers did find that most British women get their iron from eating vegetables rather than meat, which hasn’t been shown before, she told Reuters Health.
There is some previous evidence that iron intake is associated with a greater birthweight, Caulfield said. More iron means that the developing baby can get enough oxygen, she explained.
However, the current study does not prove that the pregnant moms’ higher iron intake is what caused their babies to be bigger, only that there’s some association between the two.
Low birthweight is dangerous for babies, because they’re more likely to have disabilities or die during before they’re 1 year old.
Still, that doesn’t necessarily mean women should take iron supplements during pregnancy, Alwan cautioned in an e-mail.
She suggests that pregnant women be informed about how to get enough iron in their diets, “and also how they can maximize the benefits by eating a varied diet including vitamin C-rich fruit and vegetables.”
Vitamin C helps the body absorb iron. Dried beans, spinach, brewer’s yeast and dried fruits are all good sources of iron, according to the American Heart Association.