It is often said that women hit their sexual prime after age 30. If so, it's probably because they have finally become "at home" in their bodies -- attuned to their monthly rhythms and at ease with their sexuality.
So it's ironic that Mother Nature should pick that time to reshuffle the deck: As women begin to move toward menopause, their bodies start changing again. And as their bodies change, they may need to reconsider their contraceptive options.
While the average age of menopause is 52, some women see monthly changes, such as irregular periods, as early as their late 30s.
Still, according to the U.S. National Survey of Family Growth, 26 percent of women aged 40 to 44 are fertile. Of the remaining 74 percent, roughly 39 percent are surgically sterilized (or their partners are), 22 percent have had hysterectomies and 3 percent are menopausal. The remaining 10 percent are not sexually active or were pregnant during the survey.
Some fertility experts advise women to use birth control for two years after their last period. Other doctors feel this is overly cautious.
Dr. Charles Hammond, the head of the department of obstetrics and gynecology at Duke University Medical Center in Durham, N.C., says that a woman's fertility at 45 is greatly reduced.
"If you want to stop using contraceptives," he says, "there are blood tests your doctor can administer to determine whether you've gone through menopause."
Women who need to use birth control may want to rethink their options after age 35 because the range of choices may have increased since they last considered them.
What is best for a woman in her 30s or 40s may be different from what was best for her at 20.
Still, the best birth-control method offers the most protection from unwanted pregnancies with the fewest side effects.
Throughout the world, sterilization is the most popular choice for marriedcouples over 30 -- either tubal ligation for women or vasectomy for men.
Tubal ligation, performed either abdominally or vaginally, severs the fallopian tubes, making it impossible for an egg to travel to the uterus for fertilization.
Similarly, vasectomy cuts off sperm's exit route, but is safer, less invasive and less expensive than tubal ligation.
Because they're easy to use and nearly 100 percent effective, oral contraceptives are enormously popular with women under 35.
But older women can consider using them, too.
The Food and Drug Administration proclaimed the birth-control pill safe for non-smokers over 35 who are in good health -- not obese, diabetic or hypertensive and without a history of thrombosis or heart disease.
Oral contraceptives usually contain a combination of hormones,
including estrogen and progesterone, which prevent pregnancy by suppressing ovulation.
"The pill has gotten a lot of bad press -- probably unfairly," Dr. Hammond says. "If it is associated with an increase in breast cancer, that risk is small.
"On the other hand, it's clear that the pill reduces the risk of ovarian and endometrial cancers, rheumatoid arthritis and some sexually transmitted diseases like chlamydia and gonorrhea.
"It also regularizes the menstrual cycle and reduces the amount of bleeding."
Dr. Constance Bohon, an obstetrician and gynecologist in private practice in Maryland and Washington, says that the pill does not appear to be associated with an increased risk of cardiovascular disease in older women.
"There are varying reports linking hormones and breast cancer, but there's not a definitive answer. For women with debilitating PMS [premenstrual syndrome], the pill offers tremendous benefits."
The pill may also guard against osteoporosis, prevent acne and protect against non-cancerous tumors and cysts. But it has been associated with blood clots, liver tumors, gallbladder disease, breast tenderness, weight gain and nausea.
It may not be a good choice for women with high blood pressure, migraine headaches or diabetes, and it's contra-indicated for women who have blood clots, inflamed veins, active liver disease, cancer, stroke, coronary artery disease and hyperlipemia.
Most importantly, women who smoke should not take the pill.
Also rising in acceptance is Norplant, a relatively new matchstick-size progesterone packet that is surgically embedded under the skin.
Because it's time-released internally, a woman is constantly protected from pregnancy without having to do anything. The biggest drawback is that it isn't easily removed.
"It's designed to stay in for five years, so scar tissue can develop," Dr. Bohon says. "They're inserted in no time, but removal takes 15 to 30 minutes and it hasn't been on the market long enough for doctors to have done a lot of removals."
One common side-effect associated with progesterone-only methods is irregular bleeding, which should be monitored by a physician. Dr. Bohon estimates that nearly 70 percent of Norplant users have irregular bleeding, spotting or no period at all.