Chances of pregnancy first day of fertile window

Brandi Jeter Riley and her husband, Terrence, were ready to give their 8-year-old daughter a baby sister or brother.

When Riley didn't get pregnant right away, she worried about infertility. But before seeing a specialist, she tried something she hadn't done before -- tracking her cycle and timing it right.

It was a success. Less than 2 months later, Riley, who lives in Oakland, CA, was pregnant. "Nine months later, I was giving birth to my little baby boy," she says.

"When a couple is having issues getting pregnant, the first step is to make sure they're doing it right," says Kara Manglani, a certified nurse midwife and fertility expert in New York. They need to learn about the woman's menstrual cycle and ovulation -- that time every month when one of their ovaries releases an egg.

When Is the Best Time to Get Pregnant?

"Most pregnancies result from sex that happened less than 2 days before ovulation," Manglani says. But you can get pregnant earlier or later. "Sperm can live in fertile cervical mucus for up to 5 days," she says. An egg can live up to 24 hours after ovulation.

Generally, your best chance of getting pregnant is 12-16 days before your period, says Edward Marut, MD, a reproductive endocrinologist with Fertility Centers of Illinois.

"The tricky part is identifying when ovulation occurs," Manglani says. Every woman's menstrual cycle is different. Many women think they ovulate on the 14th day of their cycle. But that's a myth. Most don't.

Try one or more of these methods to figure out when you ovulate.

Track Your Basal Body Temperature

This is your temperature when you first wake up in the morning. When you ovulate, it goes up slightly and stays up until your next period.

To track it, you'll need a basal body thermometer, which measures small changes. You can get one at most drugstores and supermarkets.

Take your temperature before you get out of bed every morning. Note the first day it goes up.

"Once you identify the day you ovulated, you can predict that ovulation will happen on or close to that day in future cycles," Manglani says.

Try an Ovulation Predictor Kit (OPK)

OPKs are at-home test kits that detect a surge in luteinizing hormone (LH), which your body releases 24-48 hours before you ovulate.

In the middle of your cycle, you'll test your urine every day for 5-10 days. When your LH goes up, it's time to start trying to conceive.

There are two types of OPKs:

Ovulation test strips. These are paper strips you dip into a cup of your urine. A few minutes later, a line shows up. Depending on how dark it is, you'll know if you're about to ovulate.

Digital ovulation tests. They're typically more expensive than test strips. With a digital test, you hold a stick under your morning stream of pee. The digital monitor tells you if you're likely to start ovulating.

You can get OPKs at many drugstores and supermarkets. Most have clear instructions and a toll-free number for questions.

OPKs are helpful if you have sex less often or you'd like to time it more precisely, Marut says, but they're not always accurate.

Use a Cycle Charting App

Phone apps can help you chart your cycle. You record details like the first day of your period, OPK results, and basal temperature. You'll get alerts when you're likely to be more fertile.

The drawback is most use a standard 28-day cycle, with ovulation on day 14, which isn't accurate for many women.

Fertility Monitors

Fertility monitors use urine test strips and a digital monitor to measure your LH and estrogen levels. They find your peak days and the few days leading up to them, and store your info over multiple cycles.

They're high-tech, but pricey -- about $200 and up. And like tracking apps, they often use a standard 28-day cycle.

Cervical Mucus Method

Hormones that control your menstrual cycle also affect your cervical mucus. The few days after your period are "dry days," with no mucus. As an egg matures, mucus develops in your vagina and enters your vaginal opening. It may be white, yellow, cloudy, or sticky.

Right before ovulation, you have "wet days," where mucus is clear and slippery and looks like egg whites. That's when you're most likely to conceive.

When to Have Sex

"Timing sex as close to ovulation as possible is important," Manglani says. Your best bet is to have sex often. Try doing it every day starting 5 days before ovulation. Keep going one day after ovulation.

Marut has a different take. Get in a routine of having sex every other day, he suggests, and don't worry about it.

Another option: Try the "sperm meets egg plan." Have sex every other day starting on day eight of your cycle. Start an OPK on day 10. "Once you have a positive result on your OPK, have sex every day for three days," Manglani says.

If you don't get pregnant in 6 months, see a doctor. "Most regular OB/GYN offices can start a fertility workup," Manglani says. Or reach out to a board-certified reproductive endocrinologist.