Q: I'm not ready to have children but would like to one day, so vasectomy and tubal ligation are out as choices for birth control. The pill has always made me feel sick and gain weight. Is there a natural approach to contraception?
-Leslie C., Norwalk, CT
A: Surgical sterilization is pretty much the only fool-proof method (besides complete abstinence) of preventing pregnancy. All of nature conspires to successful fertilization and the continuation of life. Therefore, if we want to have sex but not create offspring, we need to fool nature. Basically, natural contraception involves preventing the egg from coming into contact with fresh sperm.
The "rhythm method" of birth control is an overly simplistic way of figuring out the timing of ovulation-it counts on ovulation occurring on day 14. This is reasonably accurate; however, it is possible to take most of the guesswork out of predicting ovulation.
Once a month, an egg is released from one of the ovaries (alternating right and left ovary each month) and is ushered up through the Fallopian tubes, which connect the ovaries with the uterus. Once the egg is safely in the uterus (occasionally there is more than one egg), it has a short time to encounter and bond with live sperm. Women can get pregnant for only one 12-24 hour "window of opportunity" per month. Part of the trick is to figure out when the egg is in the uterus.
Four important signs of fertility can be expressed in the acronym SHOW. S stands for "soft" and refers to the cervix, which is located at the top of the vaginal vault, also known as the birth canal. A fertile cervix is soft, like your cheek, rather than firm. H is for "high" and means that the cervix is way up there. The neck of the cervix elongates up to two inches at menstruation to deliver the endometrial lining (menstrual blood) directly to the outside. Then, at ovulation, the neck of the cervix shortens to reduce the distance for the sperm to reach the egg. O is for "open" and refers to the opening at the end of the cervix, called the os, which is the gateway to the uterus. Usually the os is only the size of a ballpoint pen tip. However, at ovulation it may be as large as a dime for a day. This is the opening that enlarges to 10 centimeters in diameter during delivery of a baby. The fourth sign, W for "wet," is the most reliable and easiest to detect. Often, women are not aware of much vaginal or cervical discharge. For much of the month it may be minimal. Sometimes it looks white and feels a bit tacky, like glue. However, for the day of ovulation, the mucus is distinctly different: clear and stretchy, like egg white. In fact, the high protein composition of egg whites is similar to the biochemistry of ovulatory mucus, which is additionally loaded with estrogen crystals. A spike of estrogen is what drives the egg-of-the-month.
Basal body temperature is another way of tracking fertility. Besides paying attention to the position and moisture of the cervix, women can take and keep track of their temperature every morning for a year. Right before ovulation, there occurs a distinct rise of at least 0.7° F for a day.
Because the sperm can live three or even five days, the real trick is to figure out ovulation before it occurs. The solution involves abstinence or protected sex for the week before predicted ovulation. The second week of the monthly cycle is the danger zone. To play it safe in figuring out when the "danger zone" time begins, use the "Rule of 21," which involves a woman having tracked her fertility for about a year. When she has her data, she should calculate the number of days in the shortest cycle. Even if her cycles are usually 29 or 30 days, the shortest one of the year might be only 24 days.
She should take the length of her shortest cycle during the past year, and subtract the number 21. In the example above, the answer is 3. This means that after day 3 of her cycle, she enters the "danger zone" until her ovulation is complete. Most women will not be ovulating 5 days (the possible duration of the sperm's life) after day 3. However, this formula builds in a lot of buffer for early ovulation, long-living sperm, a freak short cycle, etc. Menses following ovulation by 12-16 days is standard. The actual timing of ovulation is a bit trickier to figure, but poses a splendid and useful challenge for everyone who enjoys potentially procreative sex.