Women who are overweight or obese at the time of conception are at increased risk for a postterm delivery, but that risk can be reduced if they restrict their pregnancy weight gain to a normal range, according to findings from a large database study.
Birth injury, meconium aspiration, cesarean delivery, and other complications have been linked to delivery beyond term, explained Dr. Donna R. Halloran, a St. Louis University pediatrician who presented the study results at the Southern regional meeting of the American Federation for Medical Research in New Orleans.
Researchers examined birth records linked to hospital discharge data for term singleton infants born at 42 weeks' gestation or beyond in Missouri over a 6-year period, collecting data on 8,542 postterm births to mothers without a history of diabetes, chronic hypertension, or a previous cesarean section.
After adjustment for maternal ethnicity, age, education, parity, tobacco history, Medicaid status, and infant sex, the odds of a postterm delivery were substantially elevated among mothers who were overweight (adjusted odds ratio, 1.12) or obese (adjusted odds ratio, 1.19) if they were overweight or obese at the time they became pregnant.
“The obesity epidemic is clearly having a detrimental impact on the health of this country, and pregnant women are no exception,” she said in an interview following the meeting. “Unfortunately, most women do not get preconceptual care.
“What we were pleased to find was that even if you are overweight or obese when the pregnancy begins, gaining an appropriate amount of weight (versus too much weight) reduces your risk of certain complications, specifically a postterm delivery.”
Indeed, this potential revision of risk occurred regardless of prepregnancy weight, whereas women gaining more than the recommended weight during pregnancy were 1.24 times more likely to be delivered post term.
Institute of Medicine (IOM) guidelines recommend a pregnancy weight gain of 28–40 pounds if a woman has a BMI of less than 19.8 kg/m2, 25–35 pounds for women with BMIs between 19.8 kg/m2 and 26 kg/m2, and 15–25 pounds for a woman with a prepregnancy BMI of 26 kg/m2 or greater.
Unfortunately, overweight and obese women in the Missouri study were more likely than thinner women to exceed IOM weight guidelines during pregnancy.
More than half of the 91,843 women with prepregnancy BMIs between 25 kg/m2 and 29.9 kg/m2 gained more than the amount recommended by the IOM, and 44% of the 31,147 with BMIs greater than 30 kg/m2 gained more than 25 pounds during pregnancy.
About 20% of these women were delivered post term if they were nulliparous and nearly 15% if they were multiparous, the study showed.
Physicians can help to reverse the trend of increasing postterm deliveries, even among women who are overweight or obese at conception, said Dr. Halloran.
“There are safe ways to stay healthy and limit weight gain during pregnancy.” She pointed to several studies demonstrating the effectiveness of patient education and guidance about healthy eating, exercise, and the risks associated with excessive weight gain.
Ironically, one study conducted at the University of Pittsburgh suggested less may be more with regard to interventions with overweight women, Dr. Halloran said (Int. J. Obes. Relat. Metab. Disord. 2002;26:1494–502).
In this randomized controlled study, increasingly intensive interventions as women gained weight during pregnancy were effective in limiting the percentage of normal-weight women who exceeded IOM weight guidelines, but in overweight women, 32% more exceeded weight guidelines in the intervention group than in the control group.
A simpler series of interventions was found to be effective with both overweight and normal-weight lower-income women in preventing excessive gestational weight gain, in a study from Cornell University (Am. J. Obstet. Gyn. 2004;19:530–6).
The methods used were intentionally designed to be reasonable to implement in clinical practice, and included monitoring of and education about gestational weight gain by health care professionals during prenatal visits and a series of educational mailings sent to patients with healthy eating and exercise tips, a self-monitoring guide, and a monthly motivational newsletter.
Dr. Donna R. Halloran noted that the risk of postterm delivery can be reduced if overweight/obese women restrict their pregnancy weight gain to a normal range. SAINT LOUIS UNIVERSITY