Low maternal weight gain ups preterm birth risk. (Bloody Amniotic Fluid Also More Common).

LOS ANGELES -- Gaining less than 25 pounds during pregnancy appears to be associated with more adverse outcomes than gaining more than the recommended 25-35 pounds, Dr. Laura Goetzl reported at the annual meeting of the American College of Obstetricians and Gynecologists.

She and her associates at Baylor College of Medicine, Houston, studied pregnancy outcomes in 927 women, all of whom had normal body mass during the first trimester of pregnancy.

The patients were seen at the Kelsey-Seybold Clinic in Houston from 1999 to 2000.

At the time of their deliveries, 331 of the women had gained less than the recommended 25-35 pounds, 269 had gained 25-35 pounds, and 327 had gained more than the recommended amount of weight, Dr. Goetzl said in a poster presentation at the meeting.

Low weight gain was associated with a significantly increased risk of delivery before 37 weeks of gestation. (See table.)

Bloody amniotic fluid was also more common in women who gained too little weight. Pregestational weight proved to be a stronger predictor of low birth weight than the amount of weight gained during pregnancy.

Maternal weight gain was not an independent risk factor for low birth weight after investigators controlled for gestational age, race, and infant sex.