Conception
Conception occurs when a sperm
gamete meets an
ovum, usually within the
fallopian tubes, and they successfully combine, creating a
zygote.
The zygote moves down the fallopian tube and into the
uterus where it becomes shallowly embedded in the
endometrium which lines the
uterine wall. (If this embedding does not take place both endometrium and zygote are lost at the woman’s next
menstrual cycle without her being aware conception had occurred.)
Stopping a pregnancy occurring before this embeddment is called contraception, and can be effected in any of the following ways.
Barrier methods
Barrier methods of contraception do not allow the gametes to meet. A physical barrier is placed between the penis and the cervix, stopping the semen and sperm from entering the uterus and finding a ripe ovum. Barrier methods of contraception are most effective when used in conjunction with a spermicide, and include:
Condoms
Condoms are latex (or more rarely lambskin) sheaths made to completely and snugly cover the penis during sexual intercourse. The ejaculate remains inside the condom after ejaculation and does not touch the woman at all. Condoms must be removed and disposed of directly after ejaculation.
Cervical caps
Cervical caps fit over the cervix allowing the penis to touch the vaginal walls directly, but making sure the sperm-containing ejaculate is kept from entering the uterus. A cervical cap must be fitted by a health care professional the first time, and must remain in place after ejaculation for 6 - 8 hours
Hormonal methods
The Pill
The Pill is actually a generic name for several different hormonal contraceptives. All types of the pill are made with progesterone and estrogen and fool the woman’s body into believing she is already pregnant and that there is no need to bring an ovum to ripeness. The woman taking the pill needs to take the same dose each day at the same time. Stomach upsets and antibiotics can disturb the effectiveness of the pill. If the pill is taken successfully, the woman does not ovulate, so there is no female gamete for the sperm to merge with, and the man can ejaculate into the woman without risk of pregnancy.
Injectables
Injectable hormonal contraceptives include Depo Provera and Depo Ralovera. They are delivered intramuscularly at precisely thirteen week intervals and, like the pill, fool the woman’s body into believing it is already pregnant. Depo Provera does contain estrogen, but does not contain progesterone and is therefor something regular smokers could consider trying when looking for a hormonal contraceptive, although injectable contraceptives can take the body a long time to recover from.
One side effect of Depo Provera is that mestruation often ceases after the first two or three injections and does not recur until after the course of injections is stopped.
The morning after pill
Morning After pills are for emergency contraception, and must be taken within 72 hours of the unprotected sexual activity. The morning after pills contain estrogen, progesterone, or both hormones, and work by supressing ovulation, inducing menstruation and affecting the uterine lining in such a way that the zygote cannot become embedded and so is lost with the menstral flow.
The morning after pill quite often causes nausea, vomiting, cramps, blood clots and breast soreness.
Physical and Surgical methods
IUDs
Intra-Uterine-Devices are small pieces of copper and/or plastic fitted inside a woman’s uterus by a health care professional. Some remain for as long as the woman does not wish to concieve children and some (hormonally treated ones) must be replaced on a regular basis. The specific way in which the IUD works is unknown. There have been many cases of women with IUDs becoming ill in several different ways, including perforation of the uterus and infants being delivered with IUD-related damage.
Women who have not yet had children are likely to be advised against using an IUD.
Vasectomy
A vasectomy is a fairly permanent form of contraception for males. An incision is made into the scrotum and the vas deferens (the tubes through which sperm is carried) are severed and tied off, stopping sperm ever reaching the penis.
Some vasectomies have been successfully reversed, but these are in the minority.
The surgery involved in a vasectomy is very minor and gives little discomfort.
Tubal ligation
Tubal ligation is the severing of the fallopian tubes in order to stop ova coming into the uterus and into contact with sperm. The ovaries continue to act in the normal manner, bringing ovum to ripeness monthly and releasing it, and releasing the hormones with govern the menstrual cycle.
"Natural" methods
"Natural" methods of contraception rely on observing one’s own reproductive cycle and having sexual contact only at those points in the cycle during which one is unlikely to ovulate. They include
Rhythm
The rhythm method uses a calendar and a thermometer to establish when a woman ovulates - one’s temperature rises measurably on ovulation - and predicting the dates of future ovulations from the pattern discovered.
Billings
The Billings method of contraception involves feeling the vaginal secretions each day to see how viscous (or not) they are, and establishing from this at what point in her reproductive cycle the woman is, and avoiding sex on day she is likely to be close to ovulation.