Many pregnant women take prenatal supplements. Some contain iron while others may not. The amount of iron a woman needs during pregnancy is important to discuss with her care provider.
A recent study found that taking iron supplements can reduce a woman's likelihood of developing anemia or having a baby with low birth weight.
Anemia is a condition in which the body does not produce enough red blood cells, which carry oxygen throughout the body.
Taking iron supplements also increased women's blood hemoglobin levels. Hemoglobin is the actual oxygen-carrying part of red blood cells.
The study, led by Batool A. Haider, an ScD candidate in the Departments of Epidemiology and Nutrition at Harvard School of Public Health, looked at pregnancy complications related to iron deficiencies.
The authors reviewed the current research on anemia, prenatal iron supplements and pregnancy outcomes.
They reviewed all the studies published through May 2012 in two major medical research databases and identified 48 randomized trials and 44 studies that compared populations of women.
The randomized studies included a combined 17,793 women, as well as other studies which included a combined 1.8 million women.
The researchers found that taking iron supplements increased the hemoglobin concentration in pregnant women's blood by 4.6 grams per liter compared to that of women not taking supplements.
Hemoglobin is the part of red blood cells that transports oxygen throughout the body.
Taking iron supplements also cut the risk in half for anemia, iron deficiency and iron deficiency anemia in pregnant women, compared with those not taking supplements.
Taking iron supplements also reduced the risk of having a baby with a low birth weight by 19 percent compared to those not taking iron supplements.
Meanwhile, pregnant women who had anemia in the first or second trimester were found to be 29 percent more likely to have a baby with a low birth weight and 21 percent more likely to have a preterm birth.
A preterm birth is a preemie, a baby delivered before the 37th week of pregnancy. The researchers did not find evidence that taking iron supplements reduced the risk of preterm birth.
In terms of the amount of iron supplements that made a difference, the researchers analyzed the amounts in 10 mg amounts.
For every 10 mg increase of iron per day, up to 66 mg per day, pregnant women were about 12 percent less likely to have anemia.
Also for every 10 mg increase of iron per day pregnant women took, newborns' birth weight increased by an average 15.1 grams (0.53 ounces) and risk of low birth weight decreased by 3 percent.
In addition, for each 1 gram per liter concentration of hemoglobin in the pregnant women's blood, her baby's birth weight increased by 14 grams (0.49 ounces).
The researchers did not find any relationships between iron supplements and the length of a woman's pregnancy, the length of a baby at birth or the risk of a baby being born too small for the pregnancy week when they were born.
"Daily prenatal use of iron substantially improved birth weight...probably leading to a reduction in risk of low birth weight," the researchers wrote.
However, taking too much iron can be dangerous to a pregnant woman and her baby, so women should discuss the amount of prenatal iron supplements she should take, if any, with her care provider.
According to dailyRx expert Andre Hall, MD, "Iron supplementation is an important component of a successful prenatal course." Dr. Hall, an OB/GYN at Birth and Women's Care, PA in Fayetteville, NC, was not involved in this study.
"Routinely, obstetricians check the complete blood count at three points during pregnancy to check for low hemoglobin (the cells responsible for carrying oxygen throughout the body and to the baby)," Dr. Hall said.
"These are at the initial visit, 28 weeks and 36 weeks," he said. "The goal, of course, is to catch anemia early and treat with iron supplementation where appropriate. In addition to the benefits for the baby and birth weight, an additional benefit to mom is increased energy, which is a rarity for pregnant women."
The study was published June 20 in the journal BMJ.
The research was funded by the Bill and Melinda Gates Foundation, the Saving Brains Program and Grand Challenges Canada. The authors declared no conflicts of interest.