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of the skin, and breast tenderness. Also, some women, particularly those over thirty-five years of age who smoke, may develop intravascular blood clots, liver disorders, or high blood pressure when using certain types of oral contraceptives.

Injectable Contraception

An intramuscular injection of Depo-Provera (medroxy-progesterone acetate) protects against pregnancy for three months by preventing maturation and release of a secondary oocyte. It also alters the uterine lining, making it less hospitable for a developing embryo. Because Depo-Provera is long-acting, it takes ten to eighteen months after the last injection for the effects to wear off.

Use of Depo-Provera requires a doctor's care, because of potential side effects and risks. The most common side effect is weight gain. Women with a history of breast cancer, depression, kidney disease, high blood pressure, migraine headaches, asthma, epilepsy, or diabetes, or strong family histories of these conditions, should probably not use this form of birth control.

Contraceptive ImplantContraceptive Implant ArmDepo Provera ImplantProgesterone Pill Oral CapsuleContraceptive Implant

Contraceptive Implants

A contraceptive implant is a set of small progesterone-containing capsules or rods, which are inserted surgically under the skin of a woman's arm or scapular region. The progesterone, which is released slowly from the implant, prevents ovulation in much the same way as do oral contraceptives. A contraceptive implant is effective for a period of up to five years, and its contraceptive action can be reversed by removing the device.

A large dose of high-potency estrogens can prevent implantation of a developing embryo in the uterus. Such a "morning-after pill," taken shortly after unprotected intercourse, promotes powerful contractions of smooth muscle in a woman's reproductive tract. This may dislodge and expel a fertilized egg or early embryo. However, if the embryo has already implanted, this treatment may injure it.

Describe two methods of contraception that use mechanical barriers.

What action can increase the effectiveness of chemical contraceptives?

What substances are contained in oral contraceptives?

Explain how oral contraceptives, injectable contraceptives, and contraceptive implants prevent pregnancy.

Intrauterine Devices

An intrauterine device, or IUD, is a small solid object that a physician places within the uterine cavity. An IUD interferes with implantation, perhaps by inflaming the uterine tissues (fig. 22.45e).

An IUD may be spontaneously expelled from the uterus or produce abdominal pain or excessive menstrual bleeding. It may also injure the uterus or produce other serious health problems and should be checked at regular intervals by a physician. A few babies have been born with IUDs attached to them.

Surgical Methods

Surgical methods of contraception sterilize the male or female. In the male, a physician removes a small section of each vas deferens near the epididymis and ties the cut ends of the ducts. This is a vasectomy, and it is a simple operation that produces few side effects, although it may cause some pain for a week or two.

After a vasectomy, sperm cells cannot leave the epi-didymis, thus they are excluded from the semen. However, sperm cells may already be present in portions of the ducts distal to the cuts. Consequently, the sperm count may not reach zero for several weeks.

The corresponding procedure in the female is called tubal ligation. The uterine tubes are cut and tied so that sperm cells cannot reach an egg cell.

Neither a vasectomy nor a tubal ligation changes hormonal concentrations or sex drives. These procedures,

Tubal Ligation Side Effects

shown in figure 22.46, provide the most reliable forms of contraception. Reversing them requires microsurgery.

H How does an IUD prevent pregnancy?

^9 Describe the surgical methods of contraception for a male and for a female.

Sexually Transmitted Diseases

The twenty recognized sexually transmitted diseases

(STDs) are often called "silent infections" because the early stages may not produce symptoms, especially in women (table 22.10). By the time symptoms appear, it is often too late to prevent complications or the spread of the infection to sexual partners. Because many STDs have similar symptoms, and some of the symptoms are also seen in diseases or allergies that are not sexually related, it is wise to consult a physician if one or a combination of these symptoms appears:

1. Burning sensation during urination

2. Pain in the lower abdomen

3. Fever or swollen glands in the neck

4. Discharge from the vagina or penis

5. Pain, itch, or inflammation in the genital or anal area

6. Pain during intercourse

7. Sores, blisters, bumps, or a rash anywhere on the body, particularly the mouth or genitals

8. Itchy, runny eyes

One possible complication of the STDs gonorrhea and chlamydia is pelvic inflammatory disease, in which bacteria enter the vagina and spread throughout the reproductive organs. The disease begins with intermittent cramps, followed by sudden fever, chills, weakness, and severe cramps. Hospitalization and intravenous antibiotics can stop the infection. The uterus and uterine tubes are often scarred, resulting in infertility and increased risk of ectopic pregnancy.

Acquired immune deficiency syndrome (AIDS) is a sexually transmitted disease. AIDS is a steady deterioration of the body's immune defenses and is caused by a virus. The body becomes overrun by infection and often cancer, diseases that the immune system usually conquers. The AIDS virus (human immunodeficiency virus, or HIV) is passed from one person to another in body fluids such as semen, blood, and milk. It is most frequently transmitted during unprotected intercourse or by using a needle containing contaminated blood.

D Why are sexually transmitted diseases often called "silent infections"?

^9 Why are sexually transmitted diseases sometimes difficult to diagnose?

H What are some common symptoms of sexually transmitted diseases?

Clinical Terms Related to the Reproductive Systems abortion (ah-bor'shun) Spontaneous or deliberate termination of pregnancy; a spontaneous abortion is commonly termed a miscarriage. amenorrhea (a-men"o-re'ah) Absence of menstrual flow, usually due to a disturbance in hormonal concentrations. cesarean section (se-sa're-an sek'shun) Delivery of a fetus through an abdominal incision. conization (ko"ni-za'shun) Surgical removal of a cone of tissue from the cervix for examination.

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