Improved Fetal Growth Associated With Maternal Rest in Fetuses Diagnosed With an Estimated Fetal Weight and an Abdominal Circumference Growth Velocity Less Than the 10th Percentile.

Introduction: Previous studies have demonstrated that fetuses with an estimated fetal weight (EFW) less than the 10th percentile with concomitant abdominal circumference (AC) growth velocity < 10th percentile are at increased risk for adverse perinatal outcomes.

Material and methods: This was a retrospective case series of 104 fetuses who had a prior study in which the EFW was > 10th percentile and were identified with a subsequent EFW < 10th percentile with concomitant AC growth velocity between two examinations of < 10th percentile. The AC, head circumference (HC), and femur length (FL) growth velocity was computed as follows: [(AC, HC, FL_{EFW < 10th} - AC, HC, FL_{EFW Previous Examination})/(weeks gestation_{EFW < 10th} - weeks gestation_{EFW Previous Examination})]. Growth velocity 10th and 90th percentile reference values for the AC, HC, and FL, were derived from equations published from Intergrowth-21st Project of longitudinal fetal growth protocol. Once abnormal growth was identified (EFW plus AC growth velocity < 10th percentile), the patients were asked to begin a course of complete maternal rest for 2 weeks, lying in the left lateral recumbent position. Following 2 weeks of maternal rest, the EFW percentile and the growth velocity of the AC, HC, and FL were reassessed as follows: Period 1: pre-diagnosis of an EFW > 10th percentile versus EFW < 10th percentile; Period II: diagnosis of an EFW < 10th percentile versus 2 weeks following maternal rest. The velocity values were plotted on graphs and z-scores were computed. A p-value of < 0.05 was considered significant.

Results: For Period I, 100% (N = 104) had an EFW and AC growth velocity < 10th percentile, 29% (30/104) a HC growth velocity < 10th percentile. Fifty-four percent (56/104) a FL growth velocity < 10th percentile. Period II, which evaluated growth after 2 weeks of maternal rest, demonstrated the following significant findings (p < 0.05): (1) increased EFW > 10th percentile (0% vs. 81%, 84/104); (2) increased AC growth velocity > 10th percentile (0% vs. 94%, 98/104); (3) increased HC growth velocity > 10th percentile (71%, 74/104 vs. 81%, 84/104), and FL growth velocity > 10th percentile (46%, 48/104 vs. 83%, 86/104).

Conclusion: Following maternal rest in fetuses with an EFW < 10th percentile and an AC growth velocity < 10th percentile, there was a significant increase in the EFW percentile as well as the AC, HC, and FL growth velocities.