Low maternal weight, failure to thrive in pregnancy, and adverse pregnancy outcomes.

Objective: The purpose of this study was to correlate low maternal pregravid weight, delivery weight, and poor gestational weight gain with perinatal outcomes.

Study Design: Maternal and perinatal data from January 1997 to June 2001 were obtained from a perinatal database at MetroHealth Medical Center. Low maternal weight (LMW) was defined as pregravid or delivery weight <100 pounds or body mass index (BMI) < or =19.8 kg/m(2). Low maternal weight gain was defined as <0.27 kg per week. Perinatal complication rates in these subjects were compared with those with weights of 100 to 200 pounds, normal BMI (>19.8, <26 kg/m(2)), and normal gestational weight gain (0.27-0.52 kg/wk). Chi-square and t tests were used where appropriate. P<.05 was significant.

Results: A percentage (2.6%) of 15,196 subjects began pregnancy weighing < or =100 pounds; 0.15% weighed <100 pounds at delivery and 13.2% had a pregravid BMI < or =19.8 kg/m(2). Pregravid LMW was highly correlated with ethnicity (Asians, 8.6%; Hispanics, 4.3%; Caucasians, 2.5%; African Americans, 1.9%; P<.001). Subjects with pregravid LMW were at increased risk for intrauterine growth restriction (IUGR) (relative risk [RR], 2.3, 95% CI, 1.3-4.05), and perineal tears (3rd-degree lacerations; RR, 1.8, 95% CI, 1.1-2.9), and low birth weight ([LBW] <2500 g; RR, 1.8, 95% CI, 1.1-2.9). They had a lower risk of cesarean section (RR, 0.72, 95% CI, 0.56-0.92) and preterm delivery (PTD) (RR, 1.1, 95% CI, 0.97-1.06). Pregravid BMI <19.8 kg/m(2) was associated with preterm labor (PTL) (RR, 1.22, 95% CI, 1.02-1.46), IUGR (RR, 1.67, 95% CI, 1.2-2.39), and LBW (<2500 g; RR, 1.13, 95% CI, 1.0-1.27) and was protective against cesarean delivery (RR, 0.8, 95% CI, 0.71-0.91). Delivery LMW was associated with LBW (<2500 g; RR, 2.81, 95% CI, 1.62-4.84), active-phase arrest (RR, 5.07, 95% CI, 1.85-13.9), PTL and PTD (RR, 2.5, 95% CI, 1.02-6.33, and RR, 2.45, 95% CI, 1.4-4.4, respectively), a lower gestational age at delivery (36.8 vs 38.3 wks, P<.05), and mediolateral episiotomy (RR, 9.6, 95% CI, 1.9-48.0). A percentage (0.8%) of subjects had BMI <19.8 kg/m(2) at delivery. Low delivery BMI was associated with birth weight <2500 g (RR, 1.74, 95% CI, 1.3-2.32), PTL (RR, 2.16, 95% CI, 1.45-3.19), and PTD (RR, 1.57, 95% CI, 1.18-2.11). Failure to thrive in pregnancy (weight gain <0.27 kg/wk) was associated with LBW (<1500 g; RR, 1.23, 95% CI, 1.03-1.45), <2500 g; RR, 1.22, 95% CI, 1.13-1.33), and PTL and PTD (RR, 1.2, 95% CI, 1.05-1.37, and RR, 1.11, 95% CI, 1.02-1.2, respectively).

Conclusion: Low weight and BMI at conception or delivery, as well as poor weight gain during pregnancy, are associated with LBW, prematurity, and maternal delivery complications.