Effect of recreational exercise on midtrimester placental growth.

Abstract

The purpose of our study was to test the hypothesis that regular recreational exercise increases the rate of growth in placental volume in the midtrimester of human pregnancy. Serial measurements of placental volume were obtained between the fourteenth and twenty-sixth gestational week in 18 subjects who exercised regularly throughout the midtrimester and in 16 matched controls with an ultrasonographic system equipped with a fixed-base, articulated-arm, 3.5 MHz B-mode transducer. Placental volumes were significantly greater in the women who maintained a regular exercise regimen throughout the midtrimester. At 16 weeks (mean +/- SD) volumes were 141 +/- 34 cm3 and 106 +/- 18 cm3 in the two groups. This difference increased at 20 weeks (265 +/- 67 cm3 vs 186 +/- 46 cm3) and again at 24 (410 +/- 87 cm3 vs 270 +/- 58 cm3) weeks' gestation because of a significant between-group difference in the rate of growth in placental volume over this time interval (34 +/- 8 cm3/wk vs 21 +/- cm3/wk). We conclude that the hypothesis is correct and speculate that the change in growth rate represents an adaptive response to the intermittent stimulus of a reduction in regional blood flow.