Objective: To identify predictors of pregnancy rate (PR) among women undergoing homologous IUI.
Design: Cross-sectional analysis of IUI cycles carried out from January 2000 to September 2002.
Setting: Private infertility center in Alicante, Spain.
Patient(s): Four hundred seventy women undergoing 1,010 cycles of IUI.
Intervention(s): Single IUI with ovarian stimulation using hMG.
Main outcome measure(s): Preovulatory follicles (>15 mm), motile spermatozoa count, type and duration of infertility, female age, insemination timing, and cycle number.
Result(s): Overall PR per cycle and multiple pregnancy and miscarriage rates were 9.2%, 8.6%, and 11.8%, respectively. Three significant predictors of pregnancy were identified by multiple logistic regression analysis: preovulatory follicles, spermatozoa count, and infertility duration. Interuterine insemination with three follicles almost tripled the PR with respect to only one, odds ratio (OR) = 2.89 (95% confidence interval [CI], 1.54-5.41). Compared with insemination with a motile sperm count >30 x, 20.1-30, 10.1-20, 5.1-10, and < or =5 x10(6), insemination progressively decreased the PR, from 15.3% in the highest category to 3.6% in the lowest (OR lowest/highest = 0.20 [95% CI: 0.09-0.45]), with a statistically significant dose-response trend. Infertility duration > or =3 years was marginally associated with a lower PR, OR = 0.65 (95% CI, 0.40-1.04). Overall, female age was not a significant predictor of pregnancy, and although PR slightly decreased beyond two IUI cycles and when a single IUI was performed 36-40 hours after hCG administration, results were not statistically significant.
Conclusion(s): Homologous IUI achieves the best results with two or three induced follicles, a high motile spermatozoa count, and infertility duration <3 years, irrespective of female age and fertility history.