Objective: To describe the influence of maternal weight and weight gain, placental volume and the rate of placental growth in early pregnancy on fetal dimensions measured sonographically.
Design: In a prospective study, 712 women were recruited from the antenatal clinic of the University Hospital of the West Indies. Data analysis was confined to 374 women on whom measurements of the placental volume at 14, 17 and 20 weeks gestation were complete. Measurements of maternal anthropometry and fetal size (by ultrasound) were performed. Weight gain in pregnancy between the first antenatal visit (8-10 weeks) and 20 weeks gestation, and the rate of growth of the placenta between 14-17 and 17-20 weeks gestation were calculated.
Main outcome measures: Fetal anthropometry (abdominal and head circumferences, femoral length, and biparietal diameter) at 35 weeks gestation.
Results: Lower maternal weight at the first antenatal visit was associated with a significantly smaller placental volume at 17 and 20 weeks gestation (P<0.002 and <0.0001 respectively). In all women, maternal weight gain was directly related to fetal anthropometry. Placental volume at 14 weeks gestation and the rate of growth of the placenta between 17 and 20 weeks gestation were significantly related to all four fetal measurements.
Conclusion: This study has provided evidence that both placental volume, and the rate of placental growth may influence fetal size. These effects are evident in the first half of pregnancy, and appear to be mediated through maternal weight and weight gain.