Ovulation after intravenous and intramuscular human chorionic gonadotropin.

OBJECTIVE

To define the time interval from intravenous and intramuscular hCG administration to follicular wall rupture and the endocrinologic events associated with ovulation.

DESIGN

Subjects were studied in two cycles and received hCG either 10,000 IU IM or 500 IU IV in a random sequence with an intervening spontaneous menstrual cycle.

PATIENTS

Thirty women from the University of Vermont Reproductive Endocrinology Service with unexplained, male, or cervical factor infertility.

INTERVENTIONS

Subjects underwent superovulation with clomiphene citrate followed by hCG administration when the lead follicle reached a mean diameter of 18 mm. Follicular rupture was determined by ultrasound monitoring every 2 hours starting 31 and 30 hours after intravenous and intramuscular hCG, respectively. Serum samples were obtained hourly for hormone measurements. The study was completed 2 hours after follicular rupture or 48 hours after hCG administration.

RESULTS

Twenty-five subjects received both intramuscular and intravenous hCG. The mean time to ovulation was 40.4 hours after intramuscular hCG (range, < or = 36 to > or = 48 hours) and 38.3 hours after intravenous hCG (range, 33 to > or = 48 hours). No differences were noted in the time interval to ovulation or rate of change in circulating E2 and P levels after IM versus IV hCG administration.

CONCLUSIONS

These findings suggest (1) ovulation occurs over a broad range of time after hCG administration; (2) ovulation does not occur in a more specific time interval after intravenous than intramuscular hCG; and (3) the rate of change in circulating E2 and P levels are not different after intravenous than intramuscular hCG.