Background: Evaluation of the association between estradiol (E2) levels on the day of hCG administration and pregnancy achievement in IVF has so far yielded conflicting results. The purpose of the present study was to systematically review the above association in cycles down-regulated with GnRH analogues.
Methods: Literature search was performed using Medline, Embase (1978-2004) and the Cochrane Library. Additionally, references of retrieved articles were hand-searched. Only full articles published in peer-reviewed medical journals were considered for analysis.
Results: All the eligible studies (n=9) involved the use of GnRH agonists and were retrospective. Two studies (including 191 patients) suggested that the higher the E2 levels on the day of hCG administration, the higher the probability of pregnancy. However, five studies (including 1875 patients), did not support an association between E2 levels on the day of hCG administration and pregnancy rates. Moreover, two of the studies including (1286 patients) suggested that high E2 levels on the day of hCG administration are associated with a decreased probability of pregnancy. If we consider only studies in which criteria used for administering hCG include follicular development but not E2 levels (including 2687 patients), there is no study suggesting a positive association between E2 levels on the day of hCG administration and pregnancy achievement.
Conclusions: Currently there is no high-quality evidence to support or deny the value of E2 determination on the day of hCG administration for pregnancy achievement in IVF cycles, where pituitary down-regulation is performed with GnRH agonists. Existing retrospective studies suggest that there is no positive association. However, in order to arrive at recommendations for clinical practice, there is a need to perform well-designed prospective studies in both agonist and antagonist cycles.