review is the influence of excessive gestational weight gain and overweight pregnancies on child health outcomes, reflecting recent research trends.

SHORT-TERM INFANT HEALTH OUTCOMES

Patrick Catalano provided an overview of the impact of prepregnancy maternal weight and gestational weight gain on the fetus. Specifically, he discussed preterm delivery, intrauterine growth restriction, macrosomia, and body composition. As mentioned in Chapter 2, statistical increases have occurred in prepregnancy weight in women of childbearing age. The prevalence of obesity has nearly doubled from the 1980s to early 2000, to close to 30 percent. In addition, data from MetroHealth Medical Center in Cleveland show the mean maternal weight at the time of delivery has increased to 190 lbs. in 2003, up from 170 lbs. in 1987.

Preterm Delivery

Maternal prepregnancy weight and gestational weight gain are related to preterm delivery.1 A recent meta-analysis of 13 studies published from 1980 through 1996 concluded that inadequate weight gain is associated with an increased risk of prematurity, with a possible indication specifically on inadequate gain late in pregnancy (Carmichael and Abrams, 1997). Overall, about 75 percent of preterm deliveries are not medically indicated but occur from spontaneous labor due to premature rupture of the membranes. In the past 10 years, an increased number of multiple births has also occurred, which are frequently associated with preterm deliveries. Approximately one-quarter of all preterm births are indicated on the basis of maternal complications, such as hypertension, diabetes, and preeclampsia. Women at the greatest risk for having a preterm birth are those with a history of preterm birth, with about three to four times the baseline population risk.

Analyses using the Pregnancy Nutrition Surveillance System show that the risk of preterm delivery varied by both maternal prepregnancy body mass index (BMI) and gestational weight gain (Schieve et al., 1999). The lowest risk of preterm delivery was found in women gaining between 0.6 and 1 lb per week, and the highest preterm delivery rate was to women who gained below or above these parameters. The greatest risk was to those women with a low prepregnancy BMI and a gestational weight gain of less than 0.2 lb/week. Similar results were found using the National Maternal

1

Many other factors relate to preterm delivery. More information can be found in the IOM report Preterm Birth: Causes, Consequences, and Prevention (Institute of Medicine, 2007).



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