So you've made the big decision -- you're going to start a family! But while you were certain that getting pregnant would be fast and easy, after six months of trying it's just not happening.
Could something be wrong? Of course that's always a possibility. But if you are young (between 18 and 34) and you and your partner are generally healthy, doctors say more often than not some simple problems -- with easy fixes -- may be standing in your way.
If it takes just one sperm and one egg to create a baby, why must men make so many sperm? And how many sperm are considered normal? How long do sperm live? Can they survive outside the body? Do men stop making sperm as they age? Is there anything you can do to increase sperm production or improve the health of your sperm?
WebMD takes a look at the facts about sperm and answers these and other frequently asked questions.
Among the most common: Miscalculating your most fertile time of the month.
"By far, the single most important thing stopping healthy couples from getting pregnant is they are not having intercourse at the right time -- and the reason for that is many women simply aren't calculating their ovulation time, or most fertile period, correctly," says Steven Goldstein, MD, professor of obstetrics and gynecology at NYU School of Medicine in New York City.
Goldstein says that, while most women know they must ovulate in order to conceive, many don't realize that waiting for this to happen before having sex causes them to bypass their most fertile time.
"After ovulation, an egg is only viable for about 24 hours -- so if you are waiting until you ovulate to have intercourse, chances are you are going to miss the opportunity to get pregnant that month," says Goldstein.
Since sperm can live in your reproductive tract for up to 72 hours, doctors say having sex beginning at least three days before ovulation dramatically increases your chance of conception.
"I tell my patients to start having sex a full five days before they expect to ovulate -- this way even if they are off a day or two in calculating their ovulation, the bases are still covered. It's better to have sex too early, than too late," says Sharon Winer, MD, an obstetrician at Cedars Sinai Medical Center in Los Angeles.
Indeed, a 10-year study published in the New England Journal of Medicine in 1997 found that having sex beginning six days prior to ovulation is the most conducive to achieving conception. In the same study, not one pregnancy occurred when sex took place 24 hours after ovulation.