Is medroxyprogesterone acetate (MPA) effective as emergency contraception when given 7 days after unprotected intercourse?

Medroxyprogesterone Acetate is NOT Effective as Emergency Contraception 7 Days After Intercourse

Medroxyprogesterone acetate (MPA/DMPA) should not be used as emergency contraception 7 days after unprotected intercourse—it is ineffective at this timepoint and is not recognized as an emergency contraceptive method by any major guideline.

Why MPA Does Not Work for Emergency Contraception

The CDC's U.S. Selected Practice Recommendations clearly identifies only four approved emergency contraception options in the United States 1:

1. Ulipristal acetate (30 mg single dose)
2. Levonorgestrel (1.5 mg single dose or split dose)
3. Combined estrogen-progestin (Yuzpe regimen)
4. Copper IUD

MPA/DMPA is conspicuously absent from this list because it does not function as emergency contraception.

The Critical Timing Problem

Emergency contraceptive pills must be taken within 5 days (120 hours) of unprotected intercourse to be effective 1. At 7 days post-intercourse:

• Fertilization has likely already occurred (typically within 24 hours of intercourse)
• Implantation may have begun (occurs 6-12 days after ovulation)
• The window for preventing ovulation or fertilization has closed

The mechanism of MPA is to prevent ovulation through gonadotropin suppression 2. Recent research shows MPA can suppress ovulation when given before the LH surge—specifically through cycle day 12 3. However, this is irrelevant 7 days after intercourse has already occurred.

What Actually Works at 7 Days Post-Intercourse

At 7 days after unprotected intercourse, no oral emergency contraceptive is effective. Your only option is:

• Copper IUD insertion - Can be inserted up to 7 days after intercourse (or up to 5 days after estimated ovulation, whichever is later) 1, 4
• The copper IUD is highly effective as emergency contraception and can be continued for ongoing contraception 1

The Approved Emergency Contraception Timeline

For future reference, here is the evidence-based timeline:

Within 72 hours (3 days):

• Levonorgestrel and ulipristal acetate have similar effectiveness 1
• Levonorgestrel is the drug of choice in Canada 4

72-120 hours (3-5 days):

• Ulipristal acetate is superior to levonorgestrel 1, 5, 6
• Pregnancy rates increase with levonorgestrel after 3 days 1

Up to 120 hours (5 days):

• Both oral methods can still be used, though efficacy decreases 1, 6

Up to 7 days:

• Only copper IUD is effective 4

Common Pitfall to Avoid

Do not confuse MPA's role as ongoing contraception with emergency contraception. While DMPA can be started as regular contraception when it's "reasonably certain" a woman is not pregnant 1, and recent research suggests it might work as emergency contraception if given before ovulation 3, there is zero evidence or guideline support for using it 7 days after intercourse.

The FDA label for DMPA explicitly states the first injection must be given "ONLY during the first 5 days of a normal menstrual period" to ensure the patient is not pregnant 2. This is about preventing inadvertent exposure during pregnancy, not about emergency contraception efficacy.

Bottom Line

At 7 days post-intercourse, offer copper IUD insertion if the patient desires emergency contraception. If she declines or it's beyond the window for even that, counsel about pregnancy testing in 2-3 weeks and initiate ongoing contraception if desired.