Getting Pregnant

Excerpted from
The Whole Pregnancy Handbook
By Joel M. Evans, M.D.

What you need to do to become pregnant is fairly straightforward, but it doesn't always happen right away. You may get pregnant within the first couple of months of trying, or it may take longer, but the odds are extremely good that you'll conceive within six to eight months or a year.

The Menstrual Cycle: The Mind and Body Dance

The menstrual cycle is the result of an amazing dance between a woman's brain and her reproductive organs. It happens in two phases: The first, known as the follicular (or estrogenic or proliferative) phase, leads up to and includes ovulation; the second, known as the luteal (or progestational or secretory) phase, extends from ovulation to menstruation.

The follicular phase

This first phase begins on day 1 of a menstrual cycle, which is the first day of steady bleeding in a period. During this phase, an egg matures within and is released from one of the approximately four hundred thousand follicles a woman has had since she first menstruated. The process can take anywhere from eight to thirty days, with any number of factors (diet, stress, exercise habits, etc.) contributing to its length. A stressful event in the middle of your cycle, or ongoing stress, can disrupt and lengthen the follicular phase, because the stress hormones the brain produces can interfere with the hormone signals the follicle and egg need for maturation and release.

Here's how a menstrual cycle typically unfolds. (Technically, the hormonal activity leading to ovulation begins before the period, but for simplicity's sake, I'll start with menstruation.) On the first day of your period (day 1 of the menstrual cycle), the hypothalamus, a gland in the brain, sends a hormonal message to the pituitary, a second gland, located just below the hypothalamus. When the pituitary receives the hypothalamus's message, it produces two more hormones-luteinizing hormone (LH) and follicle-stimulating hormone (FSH)-which trigger the ovaries to produce estrogen. As estrogen levels go up and ovulation approaches, a series of events occurs:

1. The pituitary produces lower levels of LH and FSH.

2. Between fifteen and twenty follicles begin to develop. Only one or-rarely-two, will become "dominant" and mature fully.

3. The lining of the uterus (the endometrium) begins to build up.

4. About five days before ovulation (for example, day 9 of a twenty-eight-day cycle), the glands that line the cervix, the canal between the uterus and vagina, begin to secrete mucus that's considered "fertile" because sperm can live in it for up to five days.

As the follicular phase continues, estrogen production increases until it reaches a peak and then drops off suddenly. The rapid drop-off tells the pituitary to increase LH production to six to ten times what it had been (this is the "LH surge" that's detected by ovulation predictor kits). Twelve to sixteen hours later, ovulation occurs. When it does, the egg pushes its way out of the follicle, and then tiny fingerlike projections called fimbria coax it into a fallopian tube. (Some women experience cramping when they ovulate, a phenomenon known as mittehchmerz. Some have a mucus "cascade," the sudden appearance of even more mucus.) On average, an egg survives between six and twelve hours in the fallopian tube-but it can survive as long as twenty-four hours.

You're most likely to conceive if sperm are already in the outer third of the fallopian tube (where fertilization typically takes place) when the egg is released. In fact, the three to five days preceding ovulation (the days when your cervical mucus production is highest) are considered very fertile. Couples should have intercourse frequently during this period, and women conceiving by artificial insemination may want to inseminate the day or two before as well as the day of ovulation.

Note: An egg released from one ovary won't necessarily travel down the fallopian tube on the same side. A chemical attraction between the egg and tube determines in which tube the egg will travel, meaning that an egg can be released from the left ovary but travel down the right fallopian tube. The practical implication of this is a woman only needs one open tube and one working ovary to get pregnant, and the ovary and tube don't have to be on the same side.

The luteal phase

After releasing a mature egg, the follicle turns into what's known as a corpus luteuvi (literally "yellow body," because it turns yellow), which immediately begins to produce a lot of progesterone and some estrogen. Progesterone is extremely important for a new pregnancy; among many functions, it triggers the final thickening of the uterine lining, creating a nutrient-rich environment to nurture an embryo. If a woman becomes pregnant, the corpus luteum will keep producing progesterone until the placenta matures and takes over-around week 11 or 12.

By one week after ovulation, the uterine lining will be thick enough to support an embryo. Assuming a twenty-eight-day cycle, an embryo conceived around day 14 will arrive in the uterus sometime after day 21. It will start to dig itself into the uterine lining (sometimes causing spotting) and by around day 25, the embryo will begin to release the pregnancy hormone HCG (human chorionic gonadotropin-this is what's measured in both urine and blood pregnancy tests). The HCG signals to the corpus luteum to stay alive and keep producing progesterone, which in turn insures that the uterus will stay thick and filled with nutrients the embryo needs to thrive.

If, however, a woman doesn't become pregnant, the corpus luteum will stop producing progesterone after twelve to sixteen days, and the uterine lining will slough off in menstrual bleeding.

In spite of the complexity of the menstrual cycle and the many natural variations that can occur, the overwhelming majority of women have cycles that are considered normal-with regularity, they produce an egg and then hormones necessary to support an embryo's growth into a healthy baby.

Peak Fertility: How to
Improve Your Chances of Conceiving

We all know what it takes to get pregnant; the only question is when to do what it takes. In its own way, your body lets you know when the time is right.

How to get pregnant

Every month, on average, a couple has between a 15 and 25 percent chance of conceiving. Even though the media is full of stories about how hard it is to get pregnant, most healthy couples-about 85 percent-will become pregnant within six to eight months of starting to have unprotected, mid-cycle sex. Many of the remaining 15 percent will get pregnant after another few months of trying. Given these statistics, when I first talk with a patient about pregnancy at a preconception visit, I simply encourage her to have sex whenever she and her partner are in the mood-which is one of the body's signs that you're in a fertile period-and the majority of my patients do conceive that way. (There's actually new data to back up this approach. In a small study, sixty-eight women who still ovulated and had had either a tubal ligation or used an IUD were asked to keep track when, in one month, they had intercourse. They also had regular blood tests to monitor their hormone production and fertility. Researchers found that the women had intercourse spontaneously 24 percent more often during the six days when their fertility, based on their hormone levels, was at its peak.)

Having said that, one reason it can take six to eight months to conceive is that couples might not be having sex when a woman is most fertile. If after a few months of untimed, unprotected sex, a patient hasn't conceived, we'll discuss how she can identify ovulation so she and her partner can time intercourse appropriately.

If your periods are regular, the simplest way to figure out approximately when you're likely to ovulate is to count back fourteen days from the day you expect to get your period. If your cycles are twenty-eight days, this would be day 14 (day 1 is the first day of your period). Keep in mind that though ovulation usually occurs fourteen days before menstruation, it can occur anywhere from twelve to sixteen days before, or days 10 to 16 of a twenty-eight-day cycle. If you use this method, you won't know the exact day you ovulate, but you'll have a good idea of the days during which you're most fertile. As I've noted, studies have shown that you're likely to conceive when you've had intercourse at least one day before ovulation. Therefore, if your cycles are regular, to be sure you're in your fertile range, begin to have intercourse once daily or every other day two or three days before you expect to ovulate and keep going through the day after you ovulate. For many this fertile range is between day 11 and day 17.

If you don't have regular cycles, have daily intercourse starting three days before the earliest possible ovulation day. For example, if your cycle varies between twenty-five and twenty-seven days, you might ovulate as early as day 11, so you'd start having sex daily on day 8 and continue through day 12. If you want to have more exact information about when you ovulate, or if your cycle varies by more than a few days, use an ovulation predictor kit or one of the other methods described here to help you pinpoint ovulation.