Published: October 2002
Publications
Progestogen-Only Emergency Contraception and Ectopic Pregnancy
Prescriber Update 23(3): 40-41
October 2002
Dr Mira Harrison-Woolrych, Senior Research Fellow,
Centre for Adverse Reactions Monitoring, Dunedin
Pregnancies occurring in women using daily progestogen-only oral contraceptive
pills are more likely to be ectopic than pregnancies in users of other contraceptive
methods. The Centre for Adverse Reactions Monitoring has received
three reports of ectopic pregnancy following use of a progestogen-only emergency
contraceptive pill. This is a reminder that women who have amenorrhoea
(or other symptoms suggestive of pregnancy) following use of progestogen-only
emergency contraception should have a pregnancy test. If the result is positive,
the possibility of ectopic pregnancy should be considered.
Physiological effects of progestogens may explain higher ectopic pregnancy risk
Low-dose daily progestogen-only oral contraceptive pills are effective at preventing pregnancy but if this method fails, pregnancies are more likely to be ectopic than those occurring among users of other contraceptive methods.1 A possible explanation is that progesterone modifies tubal function, reduces contractility and thus slows the rate of ovum or blastocyst transport. By the same mechanism, ectopic pregnancies might occur following treatment failure with a progestogen-only emergency contraceptive pill (ECP). The ECP is indicated for the prevention of pregnancy if taken within 72 hours of unprotected intercourse. In New Zealand, there are two brands of progestogen-only ECP available (Levonelle™ and Postinor-2™), both of which contain levonorgestrel.
CARM reports of ectopic pregnancy following progestogen-only ECP use
The Centre for Adverse Reactions Monitoring (CARM) has received three reports of ectopic pregnancy following use of a progestogen-only ECP. In all three cases it appears the post-coital contraception was taken as directed, and in two cases it was reported that treatment was started within 24 hours of unprotected intercourse. In one case, the patient had no other risk factors for ectopic pregnancy and had previously delivered two babies.
ECP not always effective at preventing pregnancy
A World Health Organisation (WHO) trial2 found the progestogen-only ECP method to be more effective and safer than the previous Yuzpe regimen of using combined oral contraceptives for emergency contraception. However, the progestogen-only ECP is not always 100% effective, with efficacy being higher the sooner it is taken after unprotected intercourse (see table below). It is therefore important to encourage women to seek emergency contraception as early as possible, and also to advise them that treatment failure may occur. Women who have amenorrhoea (or other symptoms suggestive of pregnancy) following ECP use should be followed up so that pregnancy can be excluded.
Effect of coitus-to-treatment interval on efficacy of progestogen-only ECP (levonorgestrel 0.75mg)2
| Time taken after intercourse | Proportion of pregnancies prevented |
|---|---|
| 24 hours or less | 95% |
| 25-48 hours | 85% |
| 49-72 hours | 58% |
The possibility of ectopic pregnancy should always be considered
One published review1 puts the total incidence of ectopic pregnancy in the United States at about 17 per 1000 reported pregnancies. Ectopic pregnancy is a potentially life-threatening condition, which should always be considered in any woman of reproductive age who presents with amenorrhoea (or abnormal vaginal bleeding) and pelvic pain or, more seriously, collapse. Women with these symptoms should have a pregnancy test performed. If this is positive and recent use of the ECP or other progestogen-only oral contraceptives has occurred, the index of suspicion is high for ectopic pregnancy.
Prescribers are also reminded to advise women about the possibility of ectopic pregnancy if contraceptive failure occurs with any oral progestogen-only method, and the importance of promptly seeking medical help if symptoms suggestive of ectopic pregnancy develop.
Competing interests (author): none declared.
Correspondence to Dr Mira Harrison-Woolrych, CARM, PO Box 913, Dunedin.
References
- McCann M, Potter L. Progestin-only oral contraception: a comprehensive review. Contraception 1994;50(6):S44-S49.
- WHO Task Force on Postovulatory Methods of Fertility Regulation. Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. Lancet 1998;352:428-433.
