The increased risk of complications for pregnant women who are not at a healthy weight has long been recognized. But new findings suggest that for women who had a BMI higher or lower than recommended during a first pregnancy, complications can surface during a second pregnancy–even if they did not occur during the first pregnancy or if the mother is at a healthy weight when she becomes pregnant a second time.
Senior author Dr. Jen Jen Chang, associate professor of epidemiology, said it is unclear why women with unhealthy weight but no complications during a first pregnancy would develop them during a second one. “Women who are over or underweight during their first pregnancy may experience permanent physiological changes that negatively affect their second baby.”
Researchers analyzed records of 121,092 women in the Missouri maternally-linked birth registry, from the years 1989-2005. They found that women who were underweight during their first pregnancy had a 20 percent increased chance of preterm birth and were 40 percent more likely to have a baby who is small for gestational age during their second pregnancy, when compared to women of healthy weight.
In addition, women who were obese when they first became pregnant were 54 percent more likely to have a large for gestational age baby, 156 percent more likely to have preeclampsia and 85 percent more likely to deliver by cesarean. Their babies were 37 percent more likely to die within the first 28 days of life.
“Our finding that obese women are at increased risk of neonatal death in a subsequent pregnancy, even if their first pregnancy was uncomplicated, has significant public health repercussions and warrants further research,” Dr. Chang said.
The researchers recommended health professionals counsel women who are in their child-bearing years on the potential problems an unhealthy weight could pose for pregnant mothers and babies.
The findings were published electronically in the June 20 issue of the American Journal of Obstetrics and Gynecology.