Ovarian follicular dynamics during conventional vs. continuous oral contraceptive use.
OBJECTIVE
The purpose of this study was to characterize ovarian follicular and endometrial development during conventional vs. continuous oral contraceptive (OC) dosing regimens, to explore follicular development during the hormone-free interval (HFI) and to examine follicular development following OC discontinuation.


METHODS
A randomized clinical trial involving 36 clinically normal healthy women between the ages of 18 and 35 years (24.4 +/- 3.9, SEM). Transvaginal ultrasonography and blood sampling were done to ascertain ovarian function.


RESULTS
Fewer follicles > 4 mm developed during continuous vs. conventional OC use (p = .006). No dominant follicles developed during continuous OC use vs. eight dominant follicles (16.1 +/- 3.3 mm) during the conventional OC regimen. Two of eight (25%) dominant follicles ovulated. All dominant follicles began development during the HFI. Following discontinuation of OC use, ovulation took approximately 5 days longer when compared to natural cycles.


CONCLUSIONS
Continuous OC regimens more effectively prevent dominant follicle development and breakthrough ovulation. The slight delay in time to ovulation following OC discontinuation and natural cycles could be attributed to suppression of follicle wave activity.
Department of Obstetrics, Gynecology and Reproductive Sciences, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W8 Canada.
Rebecca L
RL
Birtch
Olufemi A
OA
Olatunbosun
Roger A
RA
Pierson
D000293:Adolescent; D000328:Adult; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage*; D008597:Menstrual Cycle / Q000187:drug effects; D009644:Norgestrel / Q000008:administration & dosage / Q000031:analogs & derivatives*; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors; D014463:Ultrasonography
D003277:Contraceptives, Oral, Combined; D009644:Norgestrel; D016912:Levonorgestrel; C017576:norgestimate