What is the optimal protocol for Intrauterine Insemination (IUI)? A Mini Review and A Retrospective Study to Evaluate Effective Factors Influencing Pregnancy after IUI

Abstract

Background: Although it is well documented on the study of intrauterine insemination (IUI), the effectiveness of various factors on IUI treatment is inconsistent. The aim of this study is to investigate the various factors that influence IUI outcome and attempt to set up optimal protocol for IUI patients. Methods: This was a retrospective cohort study including1948 cycles (843 couples) that performed IUI between January 2012 and December 2013 in a single centre. Various factors that may affect IUI outcome were analyzed using chi-square. Moreover, we conducted multiple logistic regression to evaluate the main factors on the effects of IUI outcome. In addition, follicle growth and endometrial development relevant to conception were also assessed among protocols. Results: The clinical pregnancy rate (CPR) per cycle was 12.5% in the present study. Seven factors were identified to be associated significantly with CPR by multivariate logistic regression analysis: female age, type of infertility, ovarian stimulation protocol, preovulatory follicles, endometrial thickness, growing length of preovulatory follicle, post-washed total motile spermatozoa count (TMSC). Comparing with 11 days or less, more than 15 days for ovarian response and endometrial development before insemination induced a better success rate. Although ovarian stimulation with gonadotrophin or letrozole induced higher CPR when comparing to stimulation with clomiphene citrate or without stimulation, ovarian stimulation with letrozole was superior to gonadotrophin by its similar CPR to gonadotrophin but lower follicle number, without the risk of multiple pregnancy. Women younger than 41 years with elevated endometrial thickness inseminated with TMSC ≥ 4.0 million had better chance to obtain pregnancy. Number of treatment cycle was not a factor to affect CPR, with a stable CPR in the first four cycles. Conclusions: We conclude that women no more than 41 years old are suitable to perform at least 4 cycles of IUI before proceeding to IVF. The optimized IUI treatment requires ovarian stimulation with letrozole to induce one/two follicles and fertilize with four or more million motile spermatozoa and an elevated endometrium on day 15 or after in the cycle. Key words: infertility, intrauterine insemination, effective factors, clinical pregnancy rate.