Abstract
We assessed to what extent the standard dose of levonorgestrel (LNG), used for emergency
contraception, or a single dose (half dose), given in the follicular phase, affects
the ovulatory process during the ensuing 5-day period. Fifty-eight women were divided
into three groups according to timing of treatment. Each woman contributed with three
treatment cycles separated by resting cycles. All received placebo in one cycle, and
standard or single dose in two other cycles, in a randomized order. The diameter of
the dominant follicle determined the time of treatment. Each woman had the same diameter
assigned for all her treatments. Diameters were grouped into 33 categories: 12���14,
15���17 or 18���20 mm. Follicular rupture failed to occur during the 5-day period
in 44%, 50% and 36% of cycles with the standard, half dose and placebo, respectively.
Ovulatory dysfunction, characterized by follicular rupture associated with absent,
blunted or mistimed gonadotropin surge, occurred in 35%, 36% and 5% of standard, single
dose or placebo cycles, respectively. In conclusion, LNG can disrupt the ovulatory
process in 93% of cycles treated when the diameter of the dominant follicle is between
12 and 17 mm. It is highly probable that this mode of action fully accounts for the
contraceptive efficacy as well as the failure rate of this method. The present data
suggest that half the dose may be as effective as the standard dose.
Keywords
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Article info
Publication history
Accepted:
May 19,
2004
Received in revised form:
March 17,
2004
Received:
December 30,
2003
Identification
Copyright
© 2004 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
