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避孕 |
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避孕方法
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尽管各种各样的避孕方法在效果上各不相同和复杂程度不一而足，其原理却非常简单。如前所述，避孕的过程牵涉到输卵管内的卵子受精，进而引致受精卵发生卵裂并最终生长中的细胞团植入子宫内膜，于是妊娠便开始了。那么，显而易见，避免怀孕或避孕（contraception）涉及到通过防止排卵、阻止受精、防止植入等干预过程。这种干预过程可能有数种形式： |
1.
防止卵巢排卵（避孕药、避孕贴片、阴道环、皮下埋植杆和避孕针剂）。
2.
阻塞卵子的运行通道（输卵管闭塞）。
3.
防止精子成为精液的组成成分（输精管结扎术）。
4.
在卵子可受精的当口避免性交（安全期避孕）。
5.
防止精子进入阴道（阴茎退离、避孕套）。
6.
防止进入阴道内的精子向子宫颈移动（杀精子剂、阴道隔膜和宫颈帽）。
7.
干扰植入的过程（宫内避孕器和性交后避孕）。
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Contraception
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Methods of Contraception
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Although the various contraceptive methods differ in effectiveness and sophistication, the principle of contraception itself is quite simple. As described in a previous section, the process of conception involves the fertilization of an egg by a sperm inside one of the Fallopian tubes leading to the segmentation of the resulting new cell and the eventual implantation of a growing cell cluster in the uterus, thus starting pregnancy. Obviously then, the avoidance of pregnancy, or
contraception, involves an interference with this process by preventing
either ovulation, fertilization, or implantation. This interference can take several different forms:
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1. Preventing the release of an egg from the ovaries ("the pill", the patch, the ring,
implants, injections).
2. Preventing the passage of the egg through the Fallopian tube (tubal occlusion).
3. Preventing the sperm from becoming part of the ejaculated fluid (vasectomy).
4. Avoiding coitus at the time when an egg is available for fertilization (rhythm).
5. Preventing sperm from being deposited inside the vagina (withdrawal, condom).
6. Preventing the sperm inside the vagina from moving through and beyond the
cervix (spermicides, diaphragm, cervical cap).
7. Hindering the process of implantation
(IUDs, post-coital contraception).
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