about 100–1,000 actually make it to the egg. The sperm have proteins on their surface that match proteins on the shell of the egg and allow the sperm to bind to the shell of the egg. The sperm do not mechanically pierce the egg; they release proteins that biochemically digest a pathway through the shell, and once near the egg, bind to the egg. The egg then brings the sperm inside. There are packages of proteins just inside the wall of the egg that are released once a sperm enters. They harden the shell and prevent fertilization by more than one sperm. The fertilized egg is now called an embryo and will grow to an 8-32 cell embryo in the fallopian tube before being transported to the uterus.

Why are there so many more sperm than eggs? Because it’s a long way through the uterus and up the tubes, and because only 50 percent (of a good sperm sample) of the sperm know how to swim forward, and because some of them are barely moving, a tremendous number of sperm are needed to ensure that a few hundred will get through to the egg. Their journey is like one of you trying to swim across the Pacific Ocean. If there were 200 million of you, maybe a few hundred would make it. Imagine if you had to fertilize an egg when you finally got there! (We talk about sperm and male factor issues much more in Chapter 12.)

Putting Male and Female Parts Together

      Now that you know how all your parts work, are you ready to have a baby? Yes? Then it’s time to have sex. No, not right now. (Well, okay, if you must, but proper timing will enhance the chance for pregnancy.) So it is important to have sex when the timing is right. How do you know when the timing is right? This is more than just mood lighting and foreplay. To get pregnant, you need to be close to ovulation.

      Recognizing signs of ovulation

      It normally takes between 10 and 14 days to mature a good egg and release it, so if you have 28- to 30-day cycles, you may ovulate sometime between day 14 and day 16 of your cycle. Shorter cycles have an earlier ovulation day, and longer cycles a later ovulation day. How do you know if you’ve ovulated? Some women experience a sharp pain when they ovulate, called mittelschmertz, or have a vaginal discharge; however, these symptoms are very subjective and are not reliable indicators of ovulation. A more reliable method is correctly using an ovulation predictor kit. That said, you may be able to tell that you’re ovulating in a few simple ways, just by watching the calendar and being observant about your bodily functions.

      

Usually the mucus from your cervix increases around the time of ovulation. It also becomes very thin, clear, and stretchy; you can easily stretch it out a couple of inches. Rising estrogen levels from a developing follicle create this mucus, which is easier for sperm to swim through than your usual thicker mucus and also has an alkaline pH, which helps the sperm live longer. At other times of the month, cervical mucus is acidic. Be sure that you’re not confusing cervical mucus with semen from previous sex or increased secretions from sexual arousal.

      If you have no objection to feeling around inside your vagina, you’ll also notice that your cervix becomes softer, slightly open, and easier to locate with your fingers when you’re about to ovulate. At other times of the month, the cervix is found farther back in the uterus, feels firmer to the touch, and is tightly closed.

About 20 percent of women have pain called mittelschmertz (German for “middle pain”) when they ovulate. The pain seems to be caused by blood and fluid released from the ruptured follicle irritating the tissues around the ovary. Sometimes a small amount of vaginal bleeding occurs with ovulation, too.

      Some women have headaches around the time of ovulation, and others complain of bloating or breast pain. You’re probably already aware of your personal ovulation indicators, but you may have just never paid much attention to them; just don’t be disappointed if you don’t have these symptoms — that doesn’t mean you are not ovulating!

      Paying attention to when you ovulate is okay but unnecessary. If a woman has regular cycles every 28–32 days, she will ovulate around midcycle. If the goal is to get pregnant through intercourse, then having intercourse every other day around mid-cycle will maximize the chance of getting pregnant. You can have intercourse more frequently if you want. You do not need to worry that you are having too much intercourse. Men do not improve their chances for conception by storing sperm. They aren’t stored in the man’s body — in fact they die and are removed.

      Timing and fertility

      Timing is everything when it comes to getting pregnant. Many women miss the mark month after month because of mistaken ideas about the best time to get pregnant.

      

Sperm and eggs both have a short shelf life; eggs are capable of being fertilized for around 24 hours, and sperm can live up to four days in the proper environment, such as the fluid that fills the fallopian tubes. That means that if you don’t have sex within a few days before ovulation, you’re not going to get pregnant.

      Many women have been conditioned to believe that ovulation occurs on day 14; they have sex on days 12, 13, or 14 in hopes of hitting the right time. But the most consistent thing about your menstrual cycle should be that ovulation occurs 14 days before your period begins. So, if your cycles are 28 days, you ovulate on day 14. But if your cycles are short, say 25 days, you’re actually ovulating on day 11, and having sex starting on day 12 will be too late to achieve a pregnancy.

      On the other hand, if your cycles are long, say 34 days, you don’t ovulate until day 20. Having sex on day 14 will be way too early, since sperm don’t live for a week.

      So, timing sex correctly when you want to get pregnant is dependent on a solid knowledge of when you’re ovulating. We discuss the ways ovulation can be most accurately predicted in Chapter 6.

Sperm live longer in your body than the egg, so err on the early side when deciding when to start having sex. Every other day is enough, and there is no harm in having extra sperm around. When in doubt, just do it!

Conceiving a Baby: How Sex Should Work

      The time is right, the moon is bright, and it’s time to get pregnant. Here’s what needs to happen:

      1 It’s near ovulation; an egg is about to release from its follicle.

      2 You and your partner become aroused. Your vagina produces secretions that make it easier for the now erect penis to enter the vagina.

      3 During the man’s orgasm, several million sperm are forcefully ejaculated into the vagina. As they pass through the cervix into the uterus, the cervical mucus “filters” the sperm so that they’re ready to penetrate an egg.

      4 Your egg releases from the follicle and enters one of your fallopian tubes.

      5 The sperm swim through the uterus up to the fallopian tubes.

      6 The next day your egg meets up with several hundred sperm in the fallopian tube, and the sperm all attach themselves to the egg.

      7 One sperm breaks through the outer layer of the egg causing a chemical reaction that makes the egg immediately impenetrable to the rest of the sperm.

      8 The genetic material of the egg and sperm combine, and the newly created embryo is moved down the fallopian tube to the uterus. Cells which line the inside of the tube have hair-like projections and create a wave, much like moving a beach ball in the crowd at a football game. The embryo remains in the tube for a couple of days where is develops and then is moved into the uterus. So the tube is both a transporter and an incubator for the developing embryo.

      9 The embryo implants in the uterine wall and grows, and you miss your period.

      10 You’re