Sperm can live from two to seven days inside a woman. So although the egg may have only a short time during which it can be fertilized, sperm that a man deposited in the woman up to a week before can still fertilize the egg and cause pregnancy.
Even before a man ejaculates, his penis releases some liquid (the proper name is Cowper’s fluid, because the Cowper’s gland produces it, but it’s popularly referred to as “precum”), which serves as a lubricant to help the sperm go up the shaft of the penis. Any sperm that may not have been ejaculated during the man’s previous orgasms may be picked up by the Cowper’s fluid. Although that number is less than the millions of sperm in the ejaculate, how many sperm does an egg require for fertilization? One fast one.Because of Cowper’s fluid, a man may deposit sperm inside a woman’s vagina before he has an orgasm. That’s why the pullout, or withdrawal, method is not an effective means of preventing pregnancy.
GOING FOR A RIDE
Little finger-like appendages on the end of the fallopian tube called fimbria lead the egg into the tube, through which it makes its way into the uterus. If, during this trip, the egg encounters some sperm swimming along, then the first sperm to reach the egg and penetrate the hard outer shell, called the zona pellucida, will enter the egg and begin the life-creating process called fertilization.
A fertilized egg continues down the fallopian tube on a journey that takes about three days. During the first 30 hours, the chromosomes of the egg and the sperm merge, and the cells begin to divide. This new entity is called an embryo. When the embryo finishes its journey and enters the uterus (see Figure 1-2), it gets nourishment from uterine secretions, and the cells inside it continue to divide, causing the embryo to grow. Approximately six days after fertilization, the egg “hatches,” emerging from its hard shell and then burrowing its way into the uterine wall, or endometrium.
Illustration by Kathryn Born
FIGURE 1-2: The embryo nests in the wall of the uterus after fertilization. Happy landing!
If the egg is not fertilized, it passes through the uterus. About two weeks later, the uterus sheds its lining, the endometrium, in a process called menstruation. A new lining then begins to grow, ready to receive a fertilized egg the next month.
MAKING BABIES MAKES GOOD SEX, TOO
One more thing about sexual intercourse and its pleasures: As great a feeling as you get when having an orgasm during sexual intercourse, I think that most couples will tell you that they got even more pleasure from the intercourse they had while trying to make a baby. You get an extra kick from knowing that the possible result of this union between two people who love each other is another little human being.
BECOMING A BABY
After an embryo burrows its way into the endometrium, it grows until it has a human shape and all its organs — a process that takes about 12 weeks. At this point, the embryo is renamed a fetus. (Also, by this stage of the pregnancy, many couples give the fetus funny names — none of which, hopefully, will land on the final birth certificate.)
HOW CAN YOU TELL THAT YOU’RE PREGNANT?
During early pregnancy the only sure way is to take a test, which you can buy at your local drug store. But a woman will undergo many physical changes that will at least give an indication of a possible pregnancy, and these often occur before the most obvious sign, a missed period. (Not that all missed periods indicate a pregnancy, but if you had unprotected sex, the odds of a missed period being an indicator of pregnancy grow much stronger.) One of the first possible sign is a tenderness in the woman’s breasts. Another is morning sickness, as many women during the first trimester suffer bouts of nausea, particularly in the morning. Fatigue and more frequent urination are other signs that it’s time to buy a pregnancy test or visit your gynecologist.
The fetus grows inside the uterus until approximately nine months after the egg was first fertilized. Then, in a process called giving birth, a fully formed baby comes out of the uterus and through the vagina into the world (unless doctors have to remove the baby surgically, which is called a cesarean section, or c-section). If you want to know more about the specifics of pregnancy, pick up Pregnancy For Dummies, 4th Edition, by Joanne Stone, M.D., Keith Eddleman, M.D., and Mary Duenwald (Wiley).
So an important possible consequence of sexual intercourse is the making of a baby that will be born nine months later. Of course, giving birth to a baby is only the beginning of providing the care a child requires. Having a child is a very big responsibility — not one to be taken lightly, and certainly not one to be ignored when having sexual intercourse.
Enjoying a sensory experience
So the mechanics of sex makes babies, but the main reason that people engage in sex is for the sensory experience, the wide range of physical and emotional pleasures that a person can derive from sexual activity. You may think that these pleasures would be enough to draw people into having sex, but in fact this sensory experience has two sides, like the proverbial itch that needs to be scratched. If you don’t have sex for a period of time, and that period can be a matter of hours for some young adults to weeks for an older person, a little voice inside you tells you that the time for sex has arrived. You become aroused, or horny in the vernacular, meaning that as more and more time goes by, your desire for sex increases. Now, you can satisfy those desires without having sex with another person, called masturbation, which I cover in Chapter 16, but the preferable method of scratching this itch is to have sex with another person.
If a child wakes up in the middle of the night at an inopportune time, that is to say when his or her parents are having sex, the child is going to hear what may appear to be some very frightening sounds. But the very intense nature of those sounds is proof of how strong the sensory experience can be. Nothing surpasses the enjoyment that sex can bring.
Because the real center of all this pleasure takes place in the brain, it’s important to understand the process because here’s a case where the more you know, the better the results can be.
Understanding the Ins and Outs of the Sexual Response Cycle
The reason that sex therapists such as myself exist is due in great part to Dr. William Masters and Dr. Virginia Johnson, who studied the sexual response cycle in the late 1950s and early 1960s.
How did they study the sexual response cycle? They observed more than 10,000 sexual acts in their laboratories. Because even the most serious voyeur would probably have had enough after about the first 1,000, you can appreciate that they were really very dedicated scientists.
And scientists they were, because when I say observe, I don’t just mean watch. The people who took part in these studies were wired up so Masters and Johnson could tell exactly what was going on, including how much lubrication the woman made and the quantity of ejaculate the man released.