Obesity During Pregnancy Increases Risk of Premature Birth
Being overweight or obese is now the most common pregnancy complication in many developed countries, including the UK and the US. Women who are overweight at the time of pregnancy risk many health effects, not only for themselves, such as preeclampsia, but also for the baby, including congenital heart defects and premature birth.
The most recent study to find a link between maternal weight and the risk of having a preterm baby was conducted at McMaster University in Hamilton Canada. A team of researchers analyzed the results of 84 studies on pregnancies in both developed and developing countries. The research included data on 1,095 women.
The authors found a 30% increased risk of induced preterm birth (before 37 weeks) among overweight or obese women, after controlling for factors such as publication bias. And the heavier the woman, the higher the risk, with very obese women at a 70% greater risk than normal weight women.
Babies born between 37 and 42 weeks are called “full term.” Babies born earlier than 37 completed weeks of pregnancy are premature. In the United States, about 12.8% of babies are born prematurely.
Preterm birth and low birth weight are the leading causes of infant death and illness throughout childhood, particularly if the baby is born earlier than 32 or 33 weeks. Risks include breathing problems, lasting disabilities such as mental retardation, cerebral palsy, learning and behavioral problems, and vision and hearing loss.
Risk factors that increase the likelihood of a woman having preterm labor including high blood pressure and diabetes – both conditions linked with excess weight.
The authors suggest that overweight and obese women should have counseling before pregnancy so that they are aware of these risks and can try to modify their weight before pregnancy. They also stress the need for appropriate surveillance by health professionals during pregnancy.
"Family doctors, nurses, obstetricians, public health nurses, and dieticians are all important in delivering a consistent message,” said Sarah D. McDonald, the study’s lead author. “Women often make many positive lifestyle changes for their pregnancies to have healthier babies, so now we need to make sure that they are aware of these findings so they can optimize their weight before pregnancy.”
Sarah D McDonald, Zhen Han, Sohail Mulla, Joseph Beyene. Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses. BMJ, 2010; 341: c3428 DOI:10.1136/bmj.c3428