Contraceptive Method
Fertility can be controlled by interfering with the association between the sperm and ovum, by preventing ovulation or implantation, or by terminating an early pregnancy. Contraceptive methods may also be categorized as reversible and irreversible. Most current methods regulate fertility in women, with only few contraceptive s available for men.
Methods based on preventing contact between the germ cells include coitus interrupts (withdrawal before ejaculation), the rhythm method (no intercourse at times of the menstrual cycle, especially when an ovum is present in the oviduct), and barriers. Barriers methods include condoms, diaphragms, and cervical caps. When combined with spermicidal agents, barrier methods approach the high success rate of oral contraceptives for men. Because they also provide protection against the transmission of venereal disease and AIDS, their use has increased in recent years. Diaphragms and cervical caps seal off the opening of the cervix. Spermicidal are inserted in to the vagina. Postcoital douching is not an effective because some sperm enter the uterus and oviduct very rapidly.
Vasectomy is cutting of the two vasa differentia, and it prevents sperm from passing into the ejaculate. An increased incidence of sperm antibodies occurs following vasectomy, but its consequences are unknown. Tubal ligation is the closure of the oviducts. Restorative surgery for the reversal of a tubal ligation and a vasectomy can be performed; its success is limited.
Oral contraceptive steroids prevent ovulation by reducing LH and FSH secretion through negative feedback. Reduced secretion of LH and FSH retards follicular development. The pill’s effectiveness is also increased by adversely affecting the environment within the reproductive tract, making it unlikely for pregnancy to result even if fertilization were to occur. Exogenous estrogen and progesterone are likely to alter normal endometrial development and may contribute to their detrimental effects in the early establishment of pregnancy. Progesterone thickens cervical mucus and reduces oviductal peristalsis, impeding gamete transport.
Noncontraceptive benefits of the pill include a reduction in excessive menstrual bleeding, alleviation of premenstrual syndrome, and some protection against pelvic inflammatory disease. Adverse effects include nausea, headache, breast tenderness, water retention, and weight gain, some of which disappear after prolonged use. There is no evidence that fertility is reduced after discontinuation of the pill.
Several contraceptives act by interfering with zygote transport or implantation and cause early pregnancy termination. Among these are long-acting progesterone preparations, high doses of estrogen, and progesterone receptor antagonists, such as RU-486 (also called mifepristone). RU-486 blocks the action of the progesterone required for early pregnancy. Prostaglandins are given incombination with RU-486 to assist in the expulsion of the product of conception. The intrauterine devices (IUD) also prevent implantation by provoking sterile inflammation of the endometrium and prostaglandin production. The contraceptive efficacy of IUDs, especially those impregnated with progestins, copper, or zinc, is high. The drawbacks include a high rate of expulsion, uterine cramps, excessive bleeding, perforation of the uterus, and increased incidence of ectopic pregnancy. Established pregnancy can be interrupted by surgical means (dilation and curettage).
Contraceptive Use and Efficacy.
| Method | Estimated use (%) | Accidental pregnancy in year (%) |
| Pill | 32 | 3 |
| Female sterilization | 19 | 0.4 |
| Male sterilization | 14 | 0.15 |
| Diaphragm | 4-6 | 2-23 |
| Spermicidal | 5 | 20 |
| Rhythm | 4 | 20 |
| Intrauterine device | 3 | 6 |
| Condom | 17 | 12 |
References:
- Medical physiology, Lippincott Williams & Wilkins 3rd edi.
- Harrison’s Principles of Internal Medicine, 17th edition.
- Davidson’s Principles and Practice of Medicine, 20th Edition
- en.wikipedia.org
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