Postfertilization effect of hormonal emergency contraception

Area of Science:

• Reproductive medicine
• Pharmacology
• Medical ethics

Background:

• Hormonal emergency contraception (EC) is widely used in the US.
• Common EC methods include the Yuzpe regimen and levonorgestrel-alone formulations (Plan B).
• The precise mechanism of action for EC, particularly regarding postfertilization effects, requires further investigation.

Purpose of the Study:

• To evaluate the potential for a postfertilization effect of common hormonal emergency contraception (EC) methods.
• To explore the ethical considerations arising from the possibility of a postfertilization effect.

Main Methods:

• A comprehensive literature search of MEDLINE and review articles was conducted.
• Search terms focused on emergency contraception, postcoital contraception, postfertilization effect, and specific EC formulations.
• English-language articles published from 1966 to November 2001 were included.

Main Results:

• Both the Yuzpe regimen and Plan B can inhibit ovulation.
• Evidence suggests these EC methods may also reduce implantation probability by altering the endometrium, indicating a postfertilization effect.
• This postfertilization effect appears consistent across different phases of the menstrual cycle.

Conclusions:

• Theoretical and empirical evidence supports that both Yuzpe regimen and Plan B likely exert a postfertilization effect at times.
• This finding has significant implications for informed consent procedures.
• The potential postfertilization effect necessitates review of emergency department protocols and conscience clause considerations.