性交后避孕
那些在发生性交时没有使用任何避孕手段而又不想要孩子的女性，或察觉自己的避孕会失败的妇女，仍能够采用“性交后避孕”方法。这就意味着既可以迅速地选用铜离子缓释宫内避孕器(IUD)，也可以尽快服用紧急避孕药(emergency contraception pills ，ECPs)。紧急避孕药也称为事后避孕药。其实，这个通俗的名称非常容易让人误解，因为，性交后有5天的时间让这个女子采取避孕措施，也就是说，比次日“早晨后”有更多的宽限期。不过，越早采取措施就越有效。尤其对于强奸或乱伦中的受害者来说，这种“紧急避孕”是避免意外怀孕的最好方式，不然可能在后来则得施行流产手术。可是，紧急避孕防止不了宫外孕。
紧急避孕药（含高剂量的雌激素和/或孕激素）在市场上的成品各种各样，名称各异，必须在性交后3日或5日内服用，分两剂口服，间隔12个小时。这将防止受精卵在子宫壁的植入。这种避孕药在许多国家勿需处方便可选用，但决不是在所有的国家都是非处方药。无论如何，有越来越多来自各界的舆论压力，要求在每一个地方都要废止需要处方才能够取药的规定。可是，与此同时，一些女性经常地服用紧急避孕药，把它作为性交后的避孕手段。依据特定的品牌而异，首次剂量需要吞服2-5粒，12小时后再服一剂。可是，即便是这样，专家的咨询还是必需的，请他们准确地决定每一个牌子的紧急避孕药应该一次服用多少粒，不然，要么会避孕失败，要么它们的副作用会很大。甚至没有服药禁忌症，也可能会有令人非常厌烦的一过性副作用，象恶心和呕吐等。其他方面，也有并发症的病例报道。不管怎样，许多女性宁愿忍受这些副作用，而不愿为非意愿妊娠担惊受怕。需要强调的是，显然，既不能把这种高剂量的紧急避孕药也不该把紧急放置宫内避孕器作为经常性的避孕方式。此外，频繁地服用紧急避孕药会导致月经不规则和难以预料（的后果）。
避孕效果：相当有效。

Contraception

Methods of Contraception: Contraceptive Methods for Women

Post-coital Contraception
A woman who does not want a child, but has engaged in coitus without using any contraceptive method, or who knows that her method has failed, can still use “post-coital contraception”. This means either the prompt insertion of a copper-releasing IUD or taking emergency contraception pills (ECPs), the so-called morning-after pills. Actually, this popular term is quite misleading, since the woman has about 5 days after coitus in which to act, i.e. more time than just a “morning after”. Nevertheless, the sooner she acts, the better. Especially in cases of rape or incest, this “emergency contraception” is the best way to avoid pregnancy and thus, perhaps later, an abortion. However, emergency contraception does not necessarily prevent an ectopic pregnancy.
The pills (high dosages of estrogen and/or progestin) are marketed under various brand names and must be taken within three to five days after coitus. They are taken in two doses, 12 hours apart. This will prevent any fertilized egg from being implanted in the uterine wall. The pills are available without prescription in a number of countries, but by no means in all. However, there is growing pressure from many sides to abolish the need for a prescription everywhere. Indeed, in the meantime, some women have used regular contraceptive pills for post-coital contraception. Depending on the particular brand, they swallowed 2-5 of these pills in a single first dose and, 12 hours later, again in a second dose. However, in cases like these, expert advice is necessary to determine exactly how many pills of which brand should be taken in each dose, otherwise they may not work and/or their side effects could be severe. Even where there are no medical objections, there may be very unpleasant temporary side effects, such as nausea and vomiting. In some cases, other after-effects have been reported. However, many women would rather endure those than the worry about an unwanted pregnancy. Still, it is obvious that neither these high-dosage pills nor emergency IUD insertions can be used as regular means of contraception. Besides, a frequent use of the pills will cause a woman’s menstrual periods to become irregular and unpredictable.
Effectiveness: fairly effective