Differing fetal growth patterns in pregnancies complicated by preterm labor.

Previous studies have demonstrated diminished ultrasonic fetal growth parameters in women delivering preterm. In this study, we tested the following hypothesis: In pregnancies complicated by spontaneous preterm labor, 1) unsuccessful tocolysis is likely to be associated with diminished fetal growth, and 2) successful tocolysis is likely to occur when fetal growth is normal. Ultrasound examinations were performed in 78 pregnancies complicated by preterm labor before 35 weeks' gestation. Tocolysis was attempted unless contraindicated or unless cervical dilatation was advanced (4 cm or greater). Pregnancies delivering before 36 weeks' gestation were compared with those delivering after this gestational age. Among the 48 pregnancies delivered before 36 weeks' gestation, a significantly greater proportion had ultrasonic growth parameters lower than normal values at corresponding gestational ages. In contrast, those pregnancies that had successful tocolysis and delivered near term demonstrated a normal distribution of ultrasound growth parameters. In pregnancies complicated by preterm labor, ultrasonic documentation of diminished fetal growth may identify the subgroup at increased risk for preterm delivery.