A very small recent study has found a greater risk among obese pregnant women of not having sufficient levels of iron, which can lead to problems during birth or for their babies.
"Get to a healthy weight before attempting to conceive."
The study, led by Sarbattama Sen, MD, a neonatologist at Tufts Medical Center and an assistant professor of pediatrics at Tufts University School of Medicine, looked at the levels of iron in newborns of 30 mothers, half of whom were obese (body mass index greater than 30) and half whom were a normal weight (body mass index between 20 and 25).
Body mass index (BMI) is a ratio of a person's height to their weight and is a commonly used tool to determine whether a person is at a healthy weight.
The researchers looked at the levels of a hormone called hepcidin in mothers' blood during the second trimester. Then, after birth, the newborn babies' blood was tested for their iron levels using the umbilical cord blood.
One of hepcidin's jobs is keeping iron levels balanced. It tends to be at lower levels during pregnancy so that the mother's body transfers more iron to her baby.
But too much hepcidin can be a problem: it doesn't allow the baby to get as much iron as he or she needs.
"When there is excess hepcidin in a cell, it binds to and inhibits the function of ferroportin, the protein that allows iron to pass through the cell membrane and into the bloodstream," said senior author Simin Nikbin Meydani, DVM, PhD, director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.
The results revealed that the overweight mothers who had higher levels of hepcidin were more likely to have babies with an insufficient amount of iron at birth.
Past research has shown that obese adults produce more hepcidin than people of a healthy weight.
When a baby is born without enough iron, it can have long-term effects on the child's health and development.
Slower development in the brain and motor skills can occur when a baby does not have enough iron, because the mineral contributes to the development of the central nervous system.
The authors cautioned that more research is necessary before any recommendations are made regarding obese pregnant women's supplement needs.
If a woman is taking a prenatal vitamin daily, she should be getting approximately 27 milligrams of iron each day already, the standard amount recommended by the American Congress of Obstetricians and Gynecologists (ACOG).
The best recommendation for pregnant women, promoted by ACOG, the authors of this study and the Institute of Medicine, is to be sure a woman is at a healthy, appropriate weight before becoming pregnant and that she eats a balanced diet that does not add too much weight during pregnancy.
Women should consult their doctors regarding the optimal weight for them and the optimal weight to add during pregnancy.
"During pregnancy, women should try to eat a varied, healthy diet while taking the standard prenatal vitamins recommended by their doctors," Sen said. "Weight gain goals should be based on a woman's BMI prior to becoming pregnant."
The study was published July 9 in the Journal of Perinatalogy. The research was funded by the US Department of Agriculture, a Tufts Medical Center Research Grant, the Natalie V. Zucker Foundation for Women Scholars, the Stanley N. Gershoff Scholarship and the National Heart, Lung and Blood Institute.