Too Much Weight Gain in Pregnancy Leads to Heavy Babies
A new study shows that women who gain too much weight while they're pregnant are likely to have heavier babies as a result. We already know the fatter a baby is at birth, the more likely it is to suffer from obesity, cancer and asthma later in life.
Researchers from Children's Hospital Boston looked at mothers who had multiple pregnancies and concluded that it was the mother's weight gain, as opposed to genetic factors, that predicts birth weight. The study, published in The Lancet, stresses the importance of weight management even before a child is born.
"It's appropriate for a baby to be born with some fat, but a baby born too fat indicates that the fetus developed in an abnormal environment during the most critical nine months of life," the article's co-author, David Ludwig, director of the Optimal Weight for Life Program at Children's Hospital Boston, says in a statement.
Ludwig and his collaborator, Janet Currie, of the Department of Economics at Columbia University, looked at the birth records of all the babies who were born in Michigan and New Jersey from 1989 to 2003, excluding multiple births. They identified women who had given birth to two or more babies in that period so they could compare pregnancies. They excluded any baby born before 37 weeks of gestation or after 41, as well as mothers who had diabetes or babies who had extremely low or high birth weights. In the end, they were left with roughly 514,000 women and 1.2 million babies.
The average woman gained 30 pounds during her pregnancy, but there was a lot of variation; 12 percent of the women gained more than 44 pounds, and the same percentage of babies were 8.8 pounds or more when they were born, which is classified as high birth weight.
"When comparing between siblings to control for genetic influences, we found that increasing amounts of maternal weight gain led to the birth of progressively heavier infants," Ludwig says in the statement.
The women who gained between 44 and 49 pounds during their pregnancies were 1.7 times more likely to have high birth weight babies than those who gained between 18 and 22 pounds, and women who gained more than 53 pounds were 2.3 times more likely to do so. That pattern held even after the researchers factored out women who had smoked, those who had had C-sections and those whose pregnancies were shorter than 39 weeks or longer than 40 weeks.
The Institute of Medicine recommends that women gain 28 to 40 pounds if they are underweight when they get pregnant, 25 to 35 pounds if they are normal weight, 15 to 25 pounds if overweight and 11 to 20 pounds if obese.
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