MATERNAL UNDERWEIGHT STATUS AND INADEQUATE RATE OF WEIGHT-GAIN DURINGTHE 3RD-TRIMESTER OF PREGNANCY INCREASES THE RISK OF PRETERM DELIVERY

This study examines the differences in the pattern of weight gain acco rding to trimesters of pregnancy for women who delivered term vs. pret erm and analyzes the independent effect of prepregnancy weight status and rate of weight gain on delivering preterm. The differential effect s of these variables on the etiological pathways of prematurity (prete rm labor and preterm rupture of the amniotic membranes) were also exam ined. Data were collected prospectively from 7589 pregnant women recei ving care in public health clinics in the West Los Angeles area. Eight y percent of women identified themselves as being of Hispanic origin. Multivariate logistic regression techniques were used to isolate the r ole of each nutritional variable from other factors that may influence birth outcome. Women who delivered preterm had patterns of weight gai n similar to women delivering term infants. Underweight status (body m ass index <19.8 kg/m(2)) before pregnancy nearly doubled the likelihoo d of delivering preterm [adjusted odds ratio (AOR) 1.98, 95% confidenc e interval (CI) = 1.33, 2.98). Inadequate weight gain in the third tri mester defined as <0.34, 0.35, 0.30 and 0.30 kg/wk for underweight, no rmal weight, overweight and obese women, respectively, increased the r isk by a similar magnitude (AOR 1.91, 95% CI = 1.40, 2.61). Slight dif ferentiation of these risk factors occurred when analyzing the etiolog ical pathways of preterm birth. Preconceptional nutrition counseling a nd promotion of adequate weight gain during the third trimester of pre gnancy should be components of public health programs designed to decr ease the prevalence of preterm birth.