OBJECTIVETo compare the results of the natural cycle and ovulation induction cycle in intrauterine insemination (IUI) for infertile couples of different ages.

METHODSWe retrospectively analyzed 746 IUI cycles for 363 infertile couples, who were divided into a natural cycle (NC) and an ovulation induction cycle (OIC) group. The two groups were respectively subdivided into a < 35 yr and a > or = 35 yr age group, and, according to the drugs used, the OIC group was again divided into subgroups of clomiphene citrate + Progynova (CC + P), menopausal gonadotropin (HMG) and CC + HMG. The rates of clinical pregnancy, abortion and delivery were compared among different groups.

RESULTSThe pregnancy rate was significantly lower in the NC than in the OIC group (11.35% versus 19.61%, P < 0.01), but the rates of abortion and delivery had no significant differences between the two groups (P > 0.05), nor did the rate of clinical pregnancy among the subgroups of CC + P, HMG and CC + HMG (18.00%, 25.00% and 19.35%, P > 0.05). The < 35-year-old patients showed statistically lower rates of pregnancy and delivery in the NC than in the OIC group (P < 0.01 and P < 0.05), while the > or = 35-year-olds exhibited no significant differences in the rates of clinical pregnancy, abortion and delivery between the two groups.

CONCLUSIONThe ovulation induction cycle could achieve a higher pregnancy rate than the natural cycle in IUI, whether with CC + P, HMG or CC + HMG, particularly for the infertile patients under 35 years. But the natural cycle is preferable for the > or = 35-year-olds.