Received December 28, 1997
Accepted January 16, 1999

Introduction: The aim of this study was to compare the efficacy of hCG administration versus spontaneous LH peak in lVF in unstimulated cycles, comparing the fertilization, cleavage and pregnancy rates. Material and rnethods: ln a retrospective analysis, we studied a total of 72 oocytes collected in lVF in natural cycles from 58 patients, ali suffering from tuba] infertility; 25 oocytes were collected after spontaneous LH peak (group A) and 47 were collected after hCG administration (group B). A comparative study between the two groups was performed. Results: ln group A, we observed the fertilization of 15 oocytes (60%). Cleavage ocurred in 13 of them (86%); we performed the transfer of 13 pre-embryos, and 2 pregnancies were achieved (15,4% per transfer). ln group B, we observed the fertilization of 41 oocytes (87,2%) and cleavage of 36 (87,8%); we performed the transfer of 32 pre-embryos, and 7 pregnancies were achieved (21,9% per transfer). The fertilization rate was significantly higher for group B (p<0,01). Conclusion: The results of this study indicate that when hCG is administered before oocyte retrieval, we can perform a more efficient egg recovery procedure and achieve higher fertilization rates, in comparison with spontaneous LH peak.