In vitro fertilization treatments with the use of clomiphene citrate or letrozole

Abstract

There has been increasing interest in combining the oral agents clomiphene citrate (CC) and letrozole with gonadotropins in IVF: for poor responders to reduce the amount of gonadotropins used, and in normal responders to reduce the incidence of ovarian hyperstimulation (OHSS). In normal responders, mild stimulation with the use of CC and gonadotropins was found to decrease the number of oocytes retrieved and result in good pregnancy rates, but in most studies the cumulative pregnancy rate was lower compared with conventional ovarian stimulation when frozen embryo transfers were considered. Coadministration of letrozole and gonadotropins has mainly been used in patients with breast cancer to prevent the massive elevation of serum E concentrations with the use of standard controlled ovarian hyperstimulation. CC and letrozole have both been used with gonadotropins in poor responders and have been shown to reduce the amount of gonadotropin used without reducing the pregnancy rate. Letrozole use with gonadotropins in IVF cycles may increase endometrial receptivity by increasing integrin expression in the endometrium and by lowering estrogen concentrations to more physiologic levels.

Comparison of modified agonist, mild-stimulation and antagonist protocols for in vitro fertilization in patients with diminished ovarian reserve

“…Like clomiphene, letrozole is also commonly used in the mild stimulation protocol. 17 It reduces oestrogen production by inhibiting aromatase and has less effect on the endometrium than clomiphene. 17 In the present study, there was no significant difference in endometrial thickness between the mild stimulation group and the other two groups, suggesting that letrozole might provide better pregnancy outcomes than clomiphene.…”

Efficacy and Safety of Controlled Ovarian Stimulation With or Without Letrozole Co-administration for Fertility Preservation: A Systematic Review and Meta-Analysis

“…However, the warning letter published by the original manufacturer still limits its general acceptance. Indeed, the safety concerns related to an increased number of reported malformations in pregnancies resulting from protocols that included letrozole were based only on a single abstract (including 150 babies from 130 pregnancies, compared to a large group of spontaneous low-risk pregnancies) and never confirmed by larger and methodologically sounder studies (25)(26)(27)(28). Therefore, the concerns related to potential risks of congenital malformations have been dispelled by the scientific community, but the warning remains.…”

A Retrospective Study of Letrozole Treatment Prior to Human Chorionic Gonadotropin in Women with Polycystic Ovary Syndrome Undergoing In Vitro Fertilization at Risk of Ovarian Hyperstimulation Syndrome

“…However, the development of the dominant ovarian follicle was not be affected and the lowered E 2 level was beneficial for embryo transfer [ 21 ]. Another study also indicated that the co-administration of letrozole and gonadotropin in the IVF cycle could increase the expression of integrin in the endometrium and increased endometrial receptivity [ 22 ]. In this study, endometrial thickness was not affected by letrozole but there was an increased trend of clinical pregnancy rates [ 22 ].…”