The rise of serum creatinine levels during labor.

Serum creatinine, blood urea nitrogen and creatine phosphokinase were measured in 32 women during the last 3 weeks of pregnancy and, in a further 39 women, during and after labor. The serum creatinine increased from 61.9 +/- 0.9 to 69.8 +/- 1.8 mumol/l (mean +/- SEM) (P less than 0.05) in the third stage of labor and returned to normal by 72 h after delivery. The muscle creatine phosphokinase increased from 54 +/- 7 to 77 +/- 9.9 units (P less than 0.05) during the third stage and remained high (87 +/- 13.3 units) 72 h later. We conclude that these changes are due to muscle contraction and injury during delivery.