In the study, "Time interval from human chorionic gonadotrophin (HCG) injection to follicular rupture" by Andersen AG, Als-Nielsen B, Hornnes PJ, Franch Andersen L, published in 1995 in the journal Human Reproduction, the authors studied exactly when ovulation happened after hCg injection.
They found that the mean time interval from hCG administration to first follicular rupture was 38.3 h. The earliest was 34 hours and the latest was 46 hours after HCG injection. This information helps couples and doctors decide when to do IUI, intrauterine insemination and when to make love after hCG injections.
On average, ovulation happens 38 hours after an hCG injection, with a range of 34 to 46 hours. hCG, or human chorionic gonadotropin is usually know as the pregnancy hormone, but hCG injections are often given shortly before ovulation to stimulate the ovary to release the egg.