Mom’s weight at the start of pregnancy affects baby’s health | Yakima Valley Memorial Hospital

May 1, 2014—Women with a high body mass index (BMI) around the time they get pregnant are at increased risk of losing their baby before or soon after birth, according to a study published in JAMA.

The higher the BMI, the greater the risk, researchers found.

BMI uses height and weight to come up with a measure of body fat.

Past studies have indicated a link between maternal BMI and these events, but not all found a meaningful association.

About the study

Researchers led by Dagfinn Aune, MS, of Imperial College London, reviewed prior studies that examined the connection between a woman’s BMI and the risk of the baby’s death.

Their analysis included 38 studies that, combined, involved approximately 47,000 fetal and infant deaths. Half of the studies came from Europe. Another six each were done in North America and Australia. The rest came from Asia, Latin America and Africa.

Overall, researchers found “moderate to strong” increases in the risk of fetal death (defined as spontaneous death of a fetus during pregnancy or labor), stillbirth (defined generally as death of a fetus after 20 weeks gestation) and infant death as maternal BMI increased. But the actual number of events per 10,000 pregnancies were small.

For example:

  • For women with a BMI of 20, there were 76 fetal deaths for every 10,000 pregnancies. For women with a BMI of 30, there were 102 fetal deaths per 10,000 pregnancies.
  • For women with a BMI of 20, there were 40 stillbirths per 10,000 pregnancies. That rose to 59 stillbirths per 10,000 when the women’s BMI was 30.
  • For women with a BMI of 20, the number of perinatal deaths (defined as stillbirth or death soon after birth) was 66 per 10,000 pregnancies. That rose to 86 perinatal deaths per 10,000 pregnancies for women with a BMI of 30.

Although the link between increasing maternal BMI and fetal and infant death isn’t clear, the researchers offered several theories. For instance, excess weight and obesity are linked with a higher risk of pre-eclampsia (high blood pressure during pregnancy), gestational diabetes, type 2 diabetes and birth defects—all of which are strongly associated with the risk of fetal and infant death.

The take-home message
Women who are or plan to get pregnant should work closely with their doctor to keep their weight in a healthy range.

How much weight should you gain during pregnancy? Find guidelines here.


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