Planning to have a baby after age 35 brings with it some special concerns. Pat Tiernan, M.D., an obstetrician-gynecologist at Advocate's South Suburban Hospital, tells us more.

I'm 36. My husband and I are planning to start a family. Will I have trouble getting pregnant?

You might. A woman's fertility declines as she grows older. Fertility peaks between ages 20 and 25 and starts to decline at age 30. For example, it will take a 25-year-old woman an average of two months to conceive, compared with four months at age 35 and even longer as a woman continues to age. Other factors, including infections, endometriosis and smoking also can affect fertility. If you have not conceived within about six months of trying, you may want to talk to your doctor about various options that can improve your chances. You should know that you're not alone. More and more women are having babies later in life. In fact, first births between ages 30 and 39 have doubled in the past 15 years, and those in women over age 40 have increased by 50 percent.

What risks do I face that younger women don't?

While it may be more difficult to conceive, women over 35 can have healthy pregnancies assuming they are in good health. That said, there are some risks your doctor will discuss with you. Older women are more likely to have babies with a chromosome abnormality like Down syndrome-the likelihood is nine times greater at age 40 than at age 30. (Even then, the risk is still less than 1 percent.) Gestational diabetes and preeclampsia (pregnancy-induced high blood pressure) strike 6 percent of women over 35, compared with only 1.3 percent of women under 35. But with the right prenatal care, older women can have healthy, normal pregnancies.