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December 02, 2015

Study: Weight gain between pregnancies raises risk of stillbirths

Women who gained around 24 pounds between pregnancies faced 50 percent higher risk of stillbirth compared to women who maintained BMI

Women who have more than one child may be at greater risk of stillbirth or infant death if they gain weight between pregnancies, according to a new study by Swedish researchers.

The study, published in the journal Lancet, analyzed information from more than 450,000 women who had two pregnancies between 1992 and 2012, LiveScience reports. Researchers sought to gain a more quantitative understanding of the link between obesity and an increased risk of preterm birth, birth defects and infant mortality.

Women in the study faced a 50 percent higher risk of stillbirths in their second pregnancy if their body mass index (BMI) increased by more than four points between pregnancies – about 24 pounds for a woman of average height – compared to women whose weight remained stable between pregnancies.

Mothers who were a normal weight during their first pregnancy, but gained between 13 and 24 pounds before their second pregnancy, faced an increased risk of 27 to 60 percent for infant death within the first year of their second child's life.

The researchers found that weight gain between pregnancies was not linked to these increased risks among women who were already overweight during their first pregnancies. If those women lost weight between pregnancies, however, the risk of infant death in the child's first month of life went down 50 percent compared to overweight women who experienced no change.

The study carefully notes that overall rates of infant death or stillbirth – defined as a death of the fetus at 28 weeks of pregnancy or later – are fairly low. Just two out of 1,000 women who maintained a stable weight between pregnancies had a stillbirth, while two out of 1,000 also had an infant death. Among women who gained at least 24 pounds between pregnancies, four out of 1,000 had a stillbirth and three out of 1,000 had an infant death.

Researchers included several factors that could have accounted for stillbirths and sudden deaths, such as age, smoking habits and time between pregnancies. Particular dietary choices and alcohol use were not accounted for as part of the study's measure of pregnancy outcomes.

The study could offer significant public health insights after it was found that 15 percent of women included gained at least 13 pounds before their second pregnancy. That share may help focus efforts to promote maintaining a healthy weight or losing weight both before and between pregnancies.

While researchers did not offer a definitive reason for the link between weight gain and risk of stillbirths and infant deaths, it is believed that higher levels of inflammation in the body can lead to damaging pregnancy outcomes.

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