Predictors of twin pregnancy after ovarian stimulation and intrauterine insemination in women with unexplained infertility.

Multi-foetal gestation is a well-known, adverse outcome of infertility treatment. Maternal and obstetrical complications are more frequent in multiple pregnancies compared to singletons. The aim of this study was to determine parameters that affect the risk for multiple pregnancies after ovarian stimulation (OS) with intrauterine insemination (IUI). We retrospectively evaluated all cases of OS with IUI cycles that ended with successful clinical pregnancy. A total of 259 pregnancies were analysed (175 singletons, 63 twins and 21 triplets). Significant parameters predicting multiple pregnancies were gravidity and number of follicles at least 15 mm in diameter on day of hCG. A previous pregnancy increased the risk for multiple gestation by a factor of 1.86 (95% CI 1.03-3.37, p = 0.04). Each follicle ≥15 mm increased the odds ratio for multiple gestation by 1.3 (95% CI 1.03-1.65, p = 0.027). In conclusion, women with more than one previous pregnancy and three or more than three follicles ≥15 mm at hCG are at risk for multi-foetal pregnancy after OS and IUI.