Human plasma prekallikrein and high molecular weight kininogen decrease during parturition.

Prekallikrein and high molecular weight kininogen were measured in plasma taken from nine women during parturition. Prekallikrein decreased significantly (p less than 0.01) from 1.49 +/- 0.15 S-2302 U/ml (mean +/- SEM) in early labor to 1.26 +/- 0.13 S-2302 U/ml in the immediate postpartum period. Immunoreactive high molecular weight kininogen also significantly decreased from 76 +/- 5 micrograms/ml to 68 +/- 5 micrograms/ml one day postpartum (p less than 0.01). Both proteins rose to normal levels within two days. The data suggest that the kallikrein-kinin system is utilized during parturition.