緊急避妊薬（"morning-after" pill）使用時は子宮外妊娠が増える

英国健康事務局は緊急避妊薬の内服を飲み遅れると子宮外妊娠が増えるらしいと警告している。性交渉後可能な限り早く黄体ホルモン剤（Levonelle）を内服することと、月経が遅れた時は子宮外妊娠に注意するべきであると。

UK Warns of Ectopic Risk with 'Morning-After' Pill
By Richard Woodman
LONDON (Reuters Health) - Britain's Chief Medical Officer has warned that women who delay taking the so-called "morning-after" pill to prevent pregnancy could increase their chances of having an ectopic, or tubal, pregnancy.
In a letter to all doctors, Sir Liam Donaldson said 12 cases of ectopic pregnancy out of a total of 201 unintended pregnancies had been reported to the Committee on Safety of Medicines following failure of Schering's emergency contraceptive pill Levonelle (levonorgestrel 0.75mg).
Although widely known as the "morning-after" pill, the progestogen-only drug is actually licensed for use up to three days after unprotected sex. However, the letter makes clear that the longer women delay taking it, the less effective it becomes.
Whereas the pills prevented 95% of pregnancies when taken within the first 24 hours, this fell to 85% on the second day and as low as 58% on the third day.
The letter notes that pregnancies that occur in women taking progestogen-only pills are more likely to be ectopic--a potentially dangerous form of pregnancy in which the embryo implants in a fallopian tube rather than the womb. As the fetus grows, it can cause the tube to rupture, which can be potentially life-threatening if not treated.
The Committee on Safety of Medicines has now advised that women seek treatment as early as possible after unprotected sex and that doctors inform women that the treatment can fail.
"Women who do not experience a normal period after using Levonelle should be followed up so that pregnancy can be excluded.
"The possibility of an ectopic pregnancy should be considered, particularly in women with a previous ectopic pregnancy, fallopian tube surgery or pelvic inflammatory disease," the letter says.
A spokeswoman for Schering's UK arm said patient information leaflets already referred to the small risk of ectopic pregnancy, but the company was discussing changes with the Medicines Control Agency to make this even clearer.