Factor XII but not protein C, protein S, antithrombin III, or factor XIII is a predictor of recurrent miscarriage.

Objective: To investigate whether a decrease in the values of protein C (PC), protein S (PS), antithrombin III (ATIII), factor XII (FXII), or factor XIII (FXIII) has predictive value for subsequent miscarriages.

Methods: Prospective study. Methods: Nagoya City University Medical School. Methods: A total of 536 patients with a history of two or more first-trimester miscarriages. Methods: One hundred and twelve patients treated with low-dose aspirin were excluded from the analysis. Methods: The subsequent pregnancy outcome of 424 patients was compared for abnormal and normal levels of each parameter.

Results: There were no differences in the subsequent miscarriage rates between abnormal and normal values of PC, PS, ATIII, and FXIII. However, the rate with abnormal FXII is significantly higher than that with normal FXII.

Conclusions: A decrease in FXII (but not in PC, PS, ATIII, or FXIII) predicts subsequent miscarriage in patients with a history of first-trimester recurrent miscarriages.