Minimum time lapse between luteinizing hormone surge or human chorionic gonadotropin administration and follicular rupture.

Occurrence of ovulation was detected by laparoscopy between 22 and 47 hours following the onset of the luteinizing hormone (LH) surge in plasma (61 patients) or human chorionic gonadotropin (hCG) administration (76 patients). None of 22 patients had ovulated before the 34th hour following LH surge or hCG, as compared with 3.4% (3 of 89) and 50.0% (11 of 22) laparoscoped after 34 to 37 hours or 37 to 39 hours, respectively. Whether measured with respect to the initial rise of LH or the injection of hCG, the time lapse before ovulation was comparable. Ovulation was more frequently established at 37 to 39 hours in spontaneous cycles (10/13) than in clomiphene-treated cycles (1/9, P less than 0.01). The onset of the LH rise was found to be a more accurate criterion than the LH peak in determining the time of ovulation.