PROS1 and hyperinsulinemic hypoglycemia, familial, 4: Other risk factors for RPL were uterine malformation (160/3291 [4.9%]), parental chromosomal abnormalities (48/1198 [4%]), thyroid dysfunction (469/2254 [20.8%]), factor XII deficiency (677/2311 [29.3%]), protein S deficiency (177/2241 [7.9%]), protein C deficiency (11/2376 [0.05%]) and unexplained causes (1045/3291 [31.7%]).