When is the best time to have sex if we're trying to conceive?

Timing is everything. Sperm can live for three to five days, but the egg is around for only 12 to 24 hours. To increase the likelihood of conception, it's important to have daily intercourse in the days leading to ovulation and on the day you ovulate. A good approach is to have sex one to two days before ovulation and again on the day you ovulate. That way, there's more likely to be a healthy supply of sperm waiting in the fallopian tube when an egg is released.

Of course, exactly when a woman ovulates isn't altogether clear. It depends in part on the length of your menstrual cycle. A woman typically ovulates about 14 days before her next period — not mid-cycle, as is commonly held. If you have a 28-day cycle, which is the average, then you would ovulate about halfway through your cycle. But if you have a 35-day cycle, you would ovulate around day 21, not day 17. (Day 1 is the first day of your period.)

To determine the time when you're most likely to be fertile, try ourovulation calculator.

How do I know when I'm ovulating?

Some women can tell when they ovulate. But most women don't notice any changes at all. If you're thinking about getting pregnant, try to track your cycle for a couple of months. Some signs of ovulation include:

+ Increased vaginal discharge that takes on a wetter, egg-white-type quality

+ A slight increase (about 0.4 to 1 degree Fahrenheit) in basal body temperature, or BBT, which you can detect by taking your temperature each morning before you get out of bed, one or two days after you ovulate. You can get a good sense of your cycle if you chart your BBT for a few months.

For information on how to track these signs, see our articles on detecting ovulation and basal body temperature and cervical mucus. The bookTaking Charge of Your Fertility: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health, by Toni Weschler, can also teach you to read your body's signals.

If you still have trouble pinpointing the exact date of ovulation, you might consider trying an ovulation predictor test.

If my periods are irregular, will it be harder for me to get pregnant?

Most women have about 12 periods a year, but some have fewer and some skip months or don't get a period at all. Stress, heavy exercise, dramatic weight loss or gain — all of these can cause interruptions in your period. The more irregular your period is, the more difficult it is to predict ovulation.

Say your cycle is 28 days one month, 21 days the next month, and 32 days the following month. Keep a record of your menstrual cycles for several months. Then subtract 17 from your shortest cycle and 11 from your longest cycle. The days in between the two are the ones you're most likely to be fertile.

If your cycles are irregular and more than 35 days apart or longer, you should consider seeing your ob-gyn or a fertility specialist to check for other causes of an irregular cycle, such as polycystic ovarian syndrome (PCOS), ovarian dysfunction, thyroid disorder, excessive weight loss or an elevated prolactin level.

Can't we just try and see what happens?

Of course, you don't have to plot basal body temperature or keep complicated logs if you don't want to. You don't even need to have an orgasm to get pregnant. Try having sex at least two to three times a week consistently, and the law of averages probably will prevail.