Are oral emergency contraceptives a safe & effective form of long-term birth control?
EVIDENCE-BASED ANSWER:
Yes, but not as effective as some other methods. Annual pregnancy rates in women using pericoital levonorgestrel 150 mcg to 1 mg range from 4.9% to 8.9%; menstrual irregularity is the most common adverse effect (strength of recommendation [SOR]: B, Cochrane review of lower-quality trials).
In women younger than 35 years who have sexual intercourse 6 or fewer times per month, correct and consistent use of pericoital levonorgestrel 1.5 mg results in an annual pregnancy rate of 11% (SOR: B, one large prospective, open-label trial).
Pericoital contraception is less effective than long-acting reversible contraceptives (annual pregnancy rates of 0.05%-0.8%) or perfect use of combined oral contraceptives (0.3% annual pregnancy rate), but similar to, or better than, typical use of combined oral contraception (9%) and condoms (18%).
RECOMMENDATIONS
The Office of Population Research at Princeton University suggests that moderate repeat use of emergency contraceptives is unlikely to cause serious harm, but estimates that women using progestin-only emergency contraception on a regular basis would have a 20% chance of pregnancy in a year.3
The American College of Obstetricians and Gynecologists states that long-term use of emergency contraception is less effective than other methods and may result in higher hormone levels and more adverse effects than other established means.4
The International Consortium for Emergency Contraception concluded that there is no basis for limiting the number of times that emergency contraceptives may be used in a menstrual cycle, that emergency contraceptives are safe, and that, although they are less effective than other forms of long-term contraception, using them repeatedly is more effective than using no method.5
The Society of Obstetricians and Gynecologists of Canada states that emergency contraception is intended for occasional use as a backup method.6 The Society also notes that repeat use isn’t as effective as regular use of other forms of contraception.
The Faculty of Sexual & Reproductive Healthcare of the (British) Royal College of Obstetricians and Gynaecologists says that use of levonorgestrel can be considered even if previously used one or more times in a menstrual cycle (SOR: D, based on non-analytical studies and expert opinion).7 The organization also recommends that emergency contraceptive providers share with patients that oral emergency contraceptive methods should not be used for long-term contraception (SOR: Good Practice Point, based on clinical experience of the guideline development group).
The Guttmacher Institute reports that without contraception, approximately 85% of sexually active women become pregnant each year.8 Long-acting reversible methods, such as implants and intrauterine devices, have annual pregnancy rates of 0.05% to 0.8%. With perfect (consistent and correct) use, combined oral contraceptives have a 0.3% annual pregnancy rate, but the rate rises to 9% with typical use. Condoms, when used perfectly, are associated with a 2% annual rate of pregnancy compared with an 18% rate with typical use.
