Fetal growth trajectories and their association with maternal and child characteristics

Background: The growth of the fetus is a complex process, influenced by genetic and environmental factors. Longitudinal patterns of fetal growth are required to fully understand this process, however to date, a paucity of data exists in this area.Objective: To identify fetal growth trajectories in-utero and to assess their association with maternal and child characteristics up to 5 years postnatal.Methods: Data from 781 mother-child pairs from the ROLO longitudinal birth cohort study were analyzed. The ROLO study was a randomized control trial of a low glycemic index diet in pregnancy to prevent recurrence of macrosomia. Fetal ultrasound measurements were recorded at 20 and 34 weeks gestation, and birth weight was recorded. Abdominal circumference (AC), weight (fetal weight, or birth weight), a standardized proxy for length (femur length or birth length, individually standardized), and AC:length ratio were examined for trajectory classes using latent class trajectory mixture models. Two-, three-, four-, and five-class models were evaluated for fit, using a linear (first order) trajectory over three time-points. ANOVA and chi-square tests were applied to test associations between trajectory membership and maternal and child characteristics up to age 5.Results: For AC, two fetal growth trajectories were identified, with 29% of participants on a "slow" trajectory and 71% on a "fast" trajectory. Those on a fast trajectory had higher rates of maternal impaired glucose tolerance (28.7 versus 16.5%, p<.001) and higher rates of mean child 5-year body mass index (BMI) centiles (64th versus 58th centile, p<.05) compared to those on the slow trajectory. For estimated fetal weight, four trajectories were identified, with 4% on a "very-slow" trajectory, 63% in a "moderate-slow" trajectory, 30% in a "moderate-fast" trajectory and 3% on a "very-fast" trajectory. Mothers with a fetus on the fastest trajectory had higher antenatal serum glucose levels (p<.05), and were more likely to deliver by cesarean section (59.1 versus 20%, p<.001). At 5 years of age, children on the fastest growth trajectory had the highest mean BMI centile (86th versus 60th centile, p<.05).Conclusions: This study shows that specific fetal growth trajectories may be associated with maternal serum glucose concentrations during pregnancy, mode of delivery and child BMI at 5 years of age. Diet and lifestyle measures that target maternal glucose levels during pregnancy may have lifelong benefits for children's BMI. Identifying those on an accelerated growth trajectory during fetal life provides a unique opportunity for antenatal and infant interventions that may have long-lasting health benefits.