Effect of posture on creatinine clearance in late pregnancy and after pregnancy

To assess creatinine clearance that indicates glomerular filtration rate (GFR) and to demonstrate the effect of posture on creatinine clearance in late pregnancy compared to the non-pregnant state.

Twenty-six healthy pregnant women aged 19-30 years were studied for two sessions, first in their third trimester of pregnancy and then in a non-pregnant state at 6-12 weeks after delivery. In both sessions, creatinine clearance was assessed at three periods: the 24-h baseline, and at the end of 2-h sitting and 2-h lying (in left lateral decubitus position) periods. Urine and blood samples were collected for creatinine clearance measurement.

The results showed that the 24-h creatinine clearance in late pregnancy was 28.3% higher than that in the non-pregnant state (122.6 +/- 26.2 vs 95.3 +/- 15.1 mL/min per 1.73 m2, P < 0.001). In late pregnancy, after 2-h sitting, creatinine clearance decreased significantly (10%) compared to the 24-h baseline (122.6 +/- 26.2 vs 110.4 +/- 28.6 mL/min per 1.73 m2, P < 0.001). Creatinine clearance rose back to the high baseline level after the pregnant woman laid in left lateral decubitus for 2 h. The decrease in creatinine clearance during prolonged sitting was not seen in the non-pregnant state. At any posture, the creatinine clearance was always higher in the pregnant state than in the non-pregnant.

This study showed that creatinine clearance in late pregnancy was much higher than in the non-pregnant state, and was affected by sitting for up to 2 h. It might be wise for women to lay down in the left lateral decubitus position for a while after many hours of sitting when pregnancy is approaching its term.