The best time to have sex
Fertility experts generally recommend that you have sex at least every other day just before and after you ovulate. This is because during ovulation, the egg that has matured in your ovary is released and settles into one of your fallopian tubes. After ovulation, this egg will survive for only about 24 hours. Sperm, however, can live up to five days in a woman's reproductive tract.

Assuming a woman has a 28-day cycle and that ovulation occurs around the 14th day of her cycle, her most fertile times would occur during days 10 to 17 of her cycle. But before you apply this math, remember: Not all women have 28-day cycles. The key to timing your intercourse is knowing the length of your own cycle so you can more accurately estimate when ovulation occurs. It's also important to understand that this "fertility window" can be highly unpredictable, even if a woman's menstrual cycle is usually regular.

Ovulation Tools
Pinpointing the precise day when ovulation should occur is a bit of a challenge. There are several methods.

1. Charting your menstrual cycle. This is the easiest but least precise way to predict ovulation. Remember, a woman's cycle begins on the first day of her period and typically lasts about 28 days. The first day begins not when a woman is spotting, but when she experiences regular flow. In a 28-day cycle women may ovulate between days 10 and 17.

2. Taking your basal body temperature (BBT). To measure BBT, simply take your temperature every morning when you wake up. Chart the temperatures on a calendar. When you are ovulating, your BBT should rise about a half degree. Physical release of the ovum (egg) probably occurs on the day prior to the first temperature elevation.

3. Ovulation predictor kits. These kits work by measuring increases in your luteinizing hormone level just before ovulation. These kits are available without a prescription at your local drug store. They're easy to use, and can usually predict ovulation 24 to 36 hours in advance.
Unfortunately, no method is perfect. For more information, talk to your healthcare provider.