Let's pray to this ancient relic

THIS DI- oh no, that's actually right.

It's spelled babies so I can tell you're young.

JOHN CEEEEEEEEENA

For women, the possibility of pregnancy begins in the ovaries, those two almond-shaped glands attached to either side of the uterus. The ovaries come fully stocked. A woman is born with 1 to 2 million eggs – more than a lifetime's supply. The eggs begin dying off almost immediately and she never produces any more. Altogether, a woman probably releases about 400 eggs over the course of her reproductive years, beginning with her first period and ending with menopause (usually between ages 45 and 55). During the middle of her menstrual cycle, most likely sometime between the 12th and 16th days, an egg reaches maturity in one of her two ovaries, then is released and quickly sucked up by the opening of the nearest fallopian tube. (These two 4-inch canals lead from the ovaries to the uterus.) This release, called ovulation, starts the conception clock ticking. The average egg lives only about 24 hours, so it has to be fertilized soon for conception to happen. If your egg meets up with a healthy sperm on its way to the uterus, the two can join and begin the process of creating a new life. If not, it ends its journey at the uterus, where it either dissolves or is absorbed by the body. When pregnancy doesn't occur, the ovary eventually stops making estrogen and progesterone (hormones that help maintain a pregnancy), and the thickened lining of the uterus is shed during your period. While women are busy maturing a single egg at the leisurely pace of about one a month, men are almost constantly at work producing millions of microscopic sperm, whose sole purpose in life is to penetrate an egg. While women come complete with all of the eggs they'll ever need, men aren't born with ready-made sperm. They have to produce them on a regular basis – from start to finish it takes 64 to 72 days to create a new sperm cell. The average sperm lives only a few weeks in a man's body, and about 250 million are released with each ejaculation. That means new sperm are always in production. Sperm begin developing in the testicles, the two glands in the scrotal sac beneath the penis. The testicles hang outside a man's body because they're quite sensitive to temperature. To produce healthy sperm, they have to stay around 94 degrees Fahrenheit – about four degrees cooler than normal body temperature. The sperm are stored in a part of the testicle called the epididymis before mixing with semen just prior to ejaculation. Despite the millions of sperm produced and released in each ejaculate, only one can fertilize an egg – this is the case even for twins. The gender of the resulting embryo depends on which type of sperm burrows into the egg first. Sperm with a Y chromosome make a boy baby, and sperm with an X chromosome make a girl. Plenty of myths about how to choose a baby's sex have been circulating for centuries. Some are backed by a bit of scientific evidence, but a child's sex is pretty much randomly determined. The big moment has arrived and you're actually having sex. In addition to all the fun, your bodies are building up the tension that you hope will end in orgasm, that wonderful, pleasurable release that also has an important biological function. In men, orgasm propels sperm-rich semen into the vagina and up against the cervix, helping them to arrive in the fallopian tubes minutes later. This process, known as ejaculation, gives sperm a head start on their way to the egg. A woman's orgasm also might help conception. Some studies suggest that the wavelike contractions associated with the female O pull sperm farther into the cervix (but other research says there's no real evidence this is true). Still, why not let go and have as much fun as you can? It couldn't hurt – and just might help – your chances of getting pregnant. Many couples wonder if a particular sexual position is best for baby-making. No one knows for sure, but some experts believe the missionary position (man on top) or the rear-entry position (man behind woman, both facing the same direction) are best because both allow for deep penetration. But do whatever you like. The most important thing about sex is that you're both having a good time and you're doing it frequently enough to have live sperm in the woman's reproductive tract during ovulation. That means you should aim to make love at least every other day during the middle of your cycle. At this point, you can't do much except cross your fingers and hope, though some experts say it helps if the woman stays on her back with a pillow under her butt for 20 or 30 minutes so gravity can help the sperm get to the waiting egg. While you and your partner are cuddling, a great deal of activity is taking place inside your body. Those millions of sperm have begun their quest to find your egg, and it's not an easy journey.  The first obstacle is the acid level in your vagina, which can be deadly to sperm. Then there's your cervical mucus, which can be an impenetrable net except on the one or two dayswhen you're most fertile. Then it miraculously loosens up so a few of the strongest swimmers can get through. But that's not all – the sperm that survive still have a long road ahead. In all, they need to travel about 7 inches from the cervix through the uterus to the fallopian tubes. If they don't find an egg in the fallopian tubes at the time of intercourse, the sperm can live in the woman's reproductive tract for three to five days. Only a few dozen sperm ever make it to the egg. The rest get trapped, lost – perhaps heading up the wrong fallopian tube – or die along the way. For the lucky few who get near the egg, the race isn't over. They have to work frantically to penetrate the egg's outer shell and get inside before the others. If the hardiest of the bunch makes it through, the egg changes instantaneously so that no other sperm can get in. It's like a protective shield that clamps down over the egg at the exact moment that first sperm is safely inside. Now the real miracle begins. The egg will be fertilized within about 24 hours as the genetic material in the sperm combines with the genetic material in the egg to create a new cell that starts dividing rapidly. You're not actually pregnant until that bundle of new cells, known as the embryo, travels the rest of the way down the fallopian tube and attaches itself to the wall of your uterus. However, you can have an ectopic pregnancy if the embryo implants somewhere other than the uterus, such as the fallopian tube. An ectopic pregnancy is not viable, and you'll either need to take medication to stop it from growing or have surgery to prevent your fallopian tube from rupturing. That final leg of the trip can take another three days or so, but it may be a few more weeks until you miss a period and suspect that you're going to have a baby. If you miss your period or notice another sign of pregnancy, you can use a home pregnancy test to find out for sure if you have a little one on the way.