Effect of maternal exercise and fetoplacental growth rate on serum erythropoietin concentrations

This study was undertaken to test the null hypotheses that neither weight-bearing exercise nor fetoplacental growth has a short- or long-term effect on the maternal serum erythropoietin level.

Serial blood samples were obtained before and after exercise from seven women who exercised regularly and seven physically active controls before pregnancy and at 8, 16, 24, 32, and 38 weeks' gestation. Fetoplacental growth was assessed both in midpregnancy (ultrasound) and at birth (morphometry).

Maternal serum erythropoietin levels rose with advancing gestation in both groups. Individual patterns, however, were quite variable and not related to differences in fetoplacental growth. There were no significant between-group differences at any time point, but levels rose after exercise in mid and late pregnancy.

The highly variable, pregnancy-associated changes in maternal serum erythropoietin were unrelated to variability in fetoplacental growth or maternal hematocrit. Absolute levels of erythropoietin are not influenced by regular exercise before or during pregnancy, but small acute elevations are seen after exercise in mid and late pregnancy.