Better Sex Now: An Age-by-Age Guide to Sexual Satisfaction and Health

What You Need to Know About Fertility

In your 20s: All the stats are on your side. You have a 25 percent chance of conceiving each month. If you're younger than 25, you have a 98 percent chance of getting pregnant within a year, and the odds are still a healthy 84 percent until age 30. You're also less likely to have a miscarriage.

Just a little smoking can do big damage. "Five or six cigarettes on the weekend may affect your future ability to conceive by decreasing the oxygen supply to your eggs," says Sherman Silber, MD, director of the Infertility Center of St. Louis and author of How to Get Pregnant: The Classic Guide to Overcoming Infertility. Additionally, a British Medical Association report found that smoking can not only delay conception but can also be a primary cause of infertility.

In your 30s: Time sex right. Doing it the two days prior to ovulation gives you the greatest chance of conceiving. An ovulation-predictor kit (available in drugstores) can tell you when you're good to go by detecting surging levels of luteinizing hormone in your urine. Don't panic if you don't get pregnant right away. A 30-year-old woman has a 20 percent chance of success every month and a 65 to 75 percent chance within a year.

Weight matters. The most fertile BMI is 20 to 25. "Being underweight or overweight can make it more difficult to conceive, because body fat produces estrogen, and too little or too much can affect your fertility," says Dr. Trupin. One percent of women run out of eggs before age 40. If you're not ready for a baby yet, consider getting a follicle count from a fertility specialist. (Go to the Association of Reproductive Health Professionals at arhp.org to find an accredited one in your area.) "A vaginal ultrasound can show the number of follicles in the development stage, and that can help your doctor estimate how many eggs you have left," says Dr. Silber. A count of 15 to 30 is considered healthy. "If yours is lower than 14 and you're not planning to get pregnant within a year, consider freezing some of your eggs for future use." The test costs about $175 and typically isn't covered by insurance.

In your 40s: Every month counts. We see so many older moms these days, it's easy to think that the fertility window is still wide open. But only 5 percent of women 40 and older conceive in a month, and just 40 to 50 percent are successful after a year. Wait no longer than a few months before consulting a fertility expert. "Older eggs are more likely to have chromosomal abnormalities," says Dr. Silber. Even if you get pregnant, you have a greater chance of miscarrying. The rate rises from 34 percent in your early 40s to 53 percent after 45. The news isn't all bad. "Donor eggs are a great option, because your uterus is probably as healthy as ever," says Dr. Silber.