NEWPORT BEACH, CALIF. — Like the rest of the U.S. population, pregnant adolescents have gotten heavier since 1990, but that hasn't resulted in fewer preterm or small-for-gestational-age babies born to teenage mothers, according to data gathered on 1,187 such first-time mothers.
“They're not benefiting the babies by adding the extra weight,” Jeanelle Sheeder said in a presentation at the annual meeting of the North American Society for Pediatric and Adolescent Gynecology.
Ms. Sheeder of the University of Colorado, Denver, and her associates analyzed data on 1,187 primigravida participants who enrolled consecutively between 1990 and 2005 in the Colorado Adolescent Maternity Program (CAMP) at the university. All were 13-18 years old and of diverse racial and ethnic backgrounds.
In that 15-year time period, there were significant increases in maternal weight, body mass index, proportion of overweight or obese mothers, age, proportion of Hispanics, and rate of induced labors. “Oddly,” Ms. Sheeder noted, maternal height decreased significantly. There also were significant decreases in the rate of pregnancy-induced hypertension and in the proportion of those who were white.
No differences over time were seen, however, in any infant outcomes, including birth weight, gestational age, preterm birth rate, and proportions of infants who were small, average, or large for gestational age. On average, the babies born to this adolescent cohort were a bit smaller than babies typically born to adult women, Ms. Sheeder said.
After adjustment of the data for significant factors, including age and race or ethnicity, only the increase in maternal weight and the decrease in maternal height remained statistically significant. No other maternal or infant measures changed significantly over time. Average maternal weight increased from 124 pounds in the early 1990s to 132 pounds in 2005, an 8-pound gain. Average maternal height decreased from 5 feet 4 inches to 5 feet 3 inches. Average birth weights were 3,170 g in 1990 and 3,000 g in 2005; the difference is within a normal 200-g fluctuation seen from year to year in this population, she said.
Maternal body mass index increased from 22 kg/m
Maternal age increased from 16.1 years to 16.7 years on average. The increasing age of the primigravid adolescents in the program over time cheered the investigators. “We were happy to see that they were getting older,” she said.
When the investigators looked at the amount of weight the mothers gained during gestation, they initially were pleased that the mothers tended to gain more pounds during pregnancy as the years progressed; they hoped that this trend would translate into bigger, healthier babies.
Unlike trends in adults, however, in which both mothers and their infants have gotten bigger, in adolescents only the moms got bigger. “This leads us to believe that adolescents probably transfer less of the weight that they gain” to infants, she said, noting that studies on appropriate weight for adolescent mothers may be warranted.