The criteria for optimal down-regulation with gonadotropin-releasing hormone-agonist: a retrospective cohort study

<i>Objective</i>: The objective of this study is to investigate whether the degree of down-regulation using GnRH-agonists is associated with pregnancy outcomes. <i>Study design</i>: This retrospective analysis was performed on 2708 cycles from 2514 patients undergoing down-regulation with the luteal phase long protocol. The serum oestradiol (E2D) and luteinising hormone (LHD) levels, the diameter of the largest follicle (DLFD) and the endometrial-thickness (ENTD) after down-regulation were used to evaluate the degree of down-regulation. One-way analysis of variance with the Bonferroni adjustment, the chi-square test and multivariate logistic regression analyses were used for the statistical analysis. <i>Results</i>: The cumulative clinical pregnancy rates (CCPR) and the cumulative live birth rates (CLBR) were higher in the cycles with E2D &lt; 30 pg/ml (63.7%, OR = 1.405 (1.055–1.870) and 56.8%, OR = 1.372 (1.039–1.813)) and 30–55pg/ml (66.8%, OR = 1.439 (1.104–1.874) and 59.8%, OR = 1.397 (1.080–1.806)) than in those with E2D &gt; 55 pg/ml (62.8% and 54.7%). There was a trend towards lower CCPRs and CLBRs in the cycles with DLFD &gt; 10 mm or ENTD ≥ 6 mm; however, this difference was not significant. <i>Conclusion</i>: The degree of down-regulation is associated with ovarian response, pregnancy, and live birth. We propose the following criteria for optimal down-regulation: E2D 30-55 pg/ml, ENTD &lt; 6 mm, and no apparent ovarian activity.