Objective: To evaluate the levels of coagulation and fibrinolytic markers during the first trimester of pregnancy in women with polycystic ovary syndrome (PCOS) and determine the effects of PCOS and obesity on the levels of these hemostatic markers. Methods: A cross-sectional study was conducted in Beijing, China, on women with PCOS (n ¼ 50), healthy women (n ¼ 50), pregnant women with PCOS (n ¼ 50), and healthy pregnant women (n ¼ 50) at 12 weeks of pregnancy. Coagulation and fibrinolytic parameters were measured. Results: The interaction between PCOS and pregnancy appears to exert effects on the activities of coagulation factors VIII and X. The interaction between PCOS and obesity also seems to affect the level of von Willebrand factor. Conclusions: Pregnant women with PCOS, especially women who are obese, are observed to be in a more prohemostatic state during the first trimester.