My wife and I are starting the "let's get pregnant phase". She went to the doctor and everything looks good to go. My question is when we are done having sex, after I ejaculate into her, how long does she have to wait until she can get up, move around, and clean up? I thought someone told us to stand on your head for 20 minutes?
As hard as it is to believe (at least it seems so judging from the mail I receive), there is no necessary waiting period. Sperm from your semen is able to reach an egg in about twenty minutes if one is present.
Let's start with the basics. Each time you ejaculate, you release about a half-billion sperm. Chemicals in your semen wake the sperm up so they begin to swim. A sensor in the sperm is able to tell the sperm which direction an egg is in your wife's body, and off they go. Even though you release about two teaspoons of semen, the sperm doesn't remain in the semen. The excess semen eventually flows back out of your wife's vagina. But even then, it coats the inside of her vagina on the way out -- in other words, not all of it comes back out.
Conceiving a baby is more a matter of timing in which the odds are highly in your favor. A typical couple, trying to have a baby will have an 85% chance of finding a baby on the way in one year's time. An egg is only fertile for 24 hours after it is released, but your sperm is able to survive for up to six days inside your wife. Not all the sperm survive that long. The population will decrease each day. But so long as you had sex within six days of when she releases an egg, the odds are that she will become pregnant.
The hard part is figuring out when she is about to release an egg. A woman releases an egg 14 days before the start of her next period. But the menstruation cycle can be variable, so you don't always know exactly when the optimal time is. One myth is for the husband to "save up" having sex until the optimal day. It actually doesn't help matters for two reasons: 1) you can easily miss the optimal day, and 2) sperm don't last forever, even when they are in a suspended state in the man's body. You might have a greater quantity of semen (but not that much greater), but it might be full of more inactive sperm. The better way is to have sex regularly and frequently, say every one to three days, focusing especially on those days of the month when your wife is more interested in sex, which just happens to coincide with the release of her egg.
For more information, read the chapter on Contraceptives, but read it with an eye toward trying to cause a pregnancy than trying to prevent one.