Spontaneous ovulation rate before oocyte retrieval in modified natural cycle IVF with and without indomethacin

The objective of this retrospective analysis was to evaluate the number of spontaneous ovulations occurring before oocyte retrieval in natural cycle IVF (nIVF) with and without the use of indomethacin. A total of 121 patients who underwent modified nIVF cycle between December 2003 and July 2006 were included in the study; 171 cycles without indomethacin and 84 cycles with indomethacin, started when the leading follicle reached 14 mm in size, were compared. The number of cycles with ovulation before oocyte retrieval and the number of cycles with no oocytes at retrieval were assessed with and without indomethacin. In addition, the pregnancy rates in the two groups of patients were analysed. There were 28 cycles (16%) in which ovulation occurred before oocyte retrieval in the group where no indomethacin was used and five cycles (6%) in which ovulation occurred before retrieval in the group where indomethacin was used. There was a statistically significant association between premature ovulation and indomethacin, with an odds ratio of 3.8 (95% confidence interval, 1.2-12.3). The oocyte retrieval per started cycle was 64% without indomethacin and 76% with indomethacin (P < 0.04). The clinical pregnancy rate per embryo transfer was 14% without indomethacin and 21% with indomethacin (not significant).