Factors associated with spontaneous miscarriage risk in IUI treatment: A retrospectively cohort of 31,933 cycles

To determine the factors associated with intrauterine insemination (IUI) miscarriages and reduce the IUI miscarriage rate, a retrospective study was performed by reviewing 31,933 IUI cycles from 2006 to 2018. The overall there were 14.50% clinical pregnancies, and 16.74% miscarriages. Logistic regression revealed the following three predictive variables: females aged ≥ 35 years (odds ratio [OR] = 2.131; p < 0.001), spontaneous miscarriage history (OR = 1.513; p = 0.005), and ovarian stimulation schemes such as clomiphene citrate (CC) (OR = 1.459; p = 0.003). The natural cycle led to a lower miscarriage rate for patients without spontaneous miscarriage history both for those over 35 years old (OR = 0.402; p = 0.034) and for those under 35 years old (OR = 0.806; p = 0.017). Gonadotropin (Gn) showed the lowest miscarriage rate for patients without abortion history, though no significant differences were found. Patients under 35 with a history of miscarriage were protected from miscarriage by using CC and Gn together (OR = 0.516; p = 0.032). No significant differences were found between various ovarian protocols when patients with abortion history were aged ≥ 35 years (p = 0.606). CC + Gn showed the lowest miscarriage rate. In conclusion, the natural cycle could be suggested for infertility couples to minimize abortion risk. When ovarian induction is required, CC + Gn had the lowest miscarriage rate for women with a history of spontaneous miscarriage while Gn is more successful for individuals without such a history.