Fetal growth trajectories in Type-1 diabetic pregnancy.

OBJECTIVE To describe the individual intrauterine growth patterns of fetuses of insulin-dependent (Type-1) diabetic women and to examine determinants of overgrowth (macrosomia) and its timing. METHODS This retrospective longitudinal study examined the developmental trajectories of fetal abdominal circumference (AC) and biparietal diameter in 76 Type-1 diabetic women with singleton pregnancies. Latent class analysis was used to identify subgroups of patients with a shared fetal AC growth trajectory. Subsequently, maternal factors, including glycemic control as assessed by glycosylated hemoglobin (HbA1c), were examined to see whether they had any effect on fetal growth. RESULTS Four subgroups with different AC growth patterns were identified. Differences in birth weight between the distinct subgroups were related to the shape of the AC growth velocity curve over gestation. Acceleration of AC growth commencing before or after 25 weeks' gestation was associated with the birth of a heavy or large-for-dates baby in 94 and 56% of cases, respectively. Poor glycemic control (HbA1c > 7.0%) during the periconception period or before 12 weeks' gestation was a modest predictor of midtrimester growth in AC. Other diabetes-related factors, fetal sex, parity, or maternal weight/obesity were unrelated to the fetal growth pattern. CONCLUSION The findings suggest that an individual fetus's growth trajectory is set early in gestation and that the contemporaneous degree of maternal glycemia plays a role in determining birth weight.