Estradiol valerate pretreatment in GnRH-antagonist cycles.

We read with great interest the Commentary of Griesinger and Kolibianakis (2012) about scheduling oocyte retrieval in GnRH antagonist cycles. Recently, the results of a randomized trial by our group were published, reporting a significant decrease in oocyte retrieval during weekend days following administration of estradiol valerate in the luteal phase of the cycle prior to the stimulated cycle (Blockeel et al., 2012). The concept is interesting, since the inability to program the start of gonadotrophin stimulation in GnRH antagonist cycles and hence to minimise weekend oocyte retrieval are a major impediment to the widespread implementation of the GnRH antagonist protocol in fertility clinics. Griesinger and Kolibianakis conclude in their Commentary that no type of pretreatment aiming to allow initiation of stimulation on a certain day will avoid weekend oocyte retrieval when predefined criteria for triggering final oocyte maturation are used. We would like to comment on several aspects mentioned in this Commentary. Scheduling ovarian stimulation and oocyte retrieval in IVF is important, both for the patient, who seeks to undergo reproductive treatment at her own convenience, and for the clinic, to organise the workload. Therefore, several attempts have been made to bring the schedule of egg retrievals in a GnRH antagonist protocol under improved control. Griesinger is the first author of an interesting systematic review and meta-analysis (Griesinger et al., 2008) as well as an updated meta-analysis (Griesinger et al., 2010), describing the negative effect of the oral contraceptive pill as a pretreatment of the GnRH antagonist protocol. Briefly, besides an increased duration of stimulation and gonadotrophin consumption, the ongoing pregnancy rate was found to be significantly lower. Therefore, alternatives to scheduling ovarian stimulation need to be found, such as estradiol valerate, without the gestagen component of the oral contraceptive pill, which could indeed exert a negative impact on endometrial receptivity in the subsequent cycle (Griesinger et al., 2010). In the vast majority of normal responder patients [e.g. 83.6% reported by Borm and Mannaerts (2000) and 90% reported by Fauser et al. (2010)], the duration of the FSH