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避孕 |
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避孕方法
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儘管各種各樣的避孕方法在效果上各不相同和複雜程度不一而足，其原理卻非常簡單。如前所述，避孕的過程牽涉到輸卵管內的卵子受精，進而引致受精卵發生卵裂並最終生長中的細胞團植入子宮內膜，於是妊娠便開始了。那麼，顯而易見，避免懷孕或避孕（contraception）涉及到通過防止排卵、阻止受精、防止植入等干預過程。這種干預過程可能有數種形式： |
1.
防止卵巢排卵（避孕藥、避孕貼片、陰道環、皮下埋植杆和避孕針劑）。
2.
阻塞卵子的運行通道（輸卵管閉塞）。
3.
防止精子成為精液的組成成分（輸精管結紮術）。
4.
在卵子可受精的當口避免性交（安全期避孕）。
5.
防止精子進入陰道（陰莖退離、避孕套）。
6.
防止進入陰道內的精子向子宮頸移動（殺精子劑、陰道隔膜和宮頸帽）。
7.
干擾植入的過程（宮內避孕器和性交後避孕）。
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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: |
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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