BACKGROUNDLetrozole is the third-generation aromatase inhibitor (AI) most widely used in assisted reproduction. AIs induce ovulation by inhibiting estrogen production; the consequent hypoestrogenic state increases GnRH release and pituitary follicle-stimulating hormone (FSH) synthesis.METHODSA systematic search of the literature was performed for both prospective and retrospective studies. Meta-analyses of randomized clinical trials (RCTs) were performed for three comparisons: letrozole versus clomiphene citrate (CC), letrozole + FSH versus FSH in intrauterine insemination (IUI) and letrozole + FSH versus FSH in IVF. In the absence of RCTs, non-randomized studies were pooled.RESULTSNine studies were included in the meta-analysis. Four RCTs compared the overall effect of letrozole with CC in patients with polycystic ovary syndrome. The pooled result was not significant for ovulatory cycles (OR = 1.17; 95% CI 0.66–2.09), or for pregnancy rate per cycle (OR = 1.47; 95% CI 0.73–2.96) or for pregnancy rate per patient (OR = 1.37; 95% CI 0.70–2.71). In three retrospective studies which compared L + FSH with FSH in ovarian stimulation for IUI, the pooled OR was 1.15 (95% CI 0.78−1.71). A final meta-analysis included one RCT and one cohort study that compared letrozole + gonadotrophin versus gonadotrophin alone: the pooled pregnancy rate per patient was not significantly different (OR = 1.40; 95% CI 0.67–2.91).CONCLUSIONSLetrozole is as effective as other methods of ovulation induction. Further randomized-controlled studies are warranted to define more clearly the efficacy and safety of letrozole in human reproduction.

This three-variable model can help to identify patients at high-risk for high-order multiple pregnancy in ovulation induction cycles.

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Infertility is a common problem presented by patients with endometriosis. At present, whichever treatment is chosen, half of patients with advanced stages of the disease will remain infertile afterwards. This observational study looked at the reproductive outcome achieved after treating a group of 825 patients aged between 20 and 40 years with endometriosis-associated infertility during the period 2001-2008. Of the 483 patients who had surgery as the primary option, 262 became pregnant (54.2%). Among the patients who did not become pregnant, 144 underwent 184 IVF cycles and 56 additional pregnancies were obtained (30.4% clinical pregnancy rate per retrieval). It is notable that, before any treatment, patients with endometriosis had a poorer ovarian reserve than the control group. The combined strategy of endoscopic surgery and subsequent IVF led to a total of 318 pregnancies, which represents a combined clinical pregnancy rate of 65.8%. This percentage is significantly higher than that obtained with surgery alone (P < 0.0001), with 173 patients who were not operated on and who went to IVF as the primary option (P < 0.0001) and with 169 patients who had no treatment and achieved 20 spontaneous pregnancies (P < 0.0001).