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 µmol/l (mean±SEM) (P<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<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.