Pregnancy at 20, 30, 40

Most experts would say there's no one right time to start a family. But there are both advantages and disadvantages to giving birth at different ages: In your 20s, for instance, you'll have more energy to run after and care for your child but fewer financial resources and less personal life experience on which to draw; in your late 30s and 40s you may be more established financially but have a tougher time getting and staying pregnant and, afterward, keeping up with an active baby and toddler.

What follows is a look at the pros and cons of pregnancy at different ages.

Laura Flynn McCarthy writes often about women's health. She lives in New Hampshire with her husband and their two sons.

Ages 20 to 24
YOUR BODY

These are your most fertile years. Your periods are probably regular, and most, if not all, of them are ovulatory. Even now, however, you may not conceive exactly when you want to. The average woman between 20 and 24 years old has about a 20 percent chance each month of getting pregnant when she has unprotected intercourse.

Once you do conceive, your blood pressure will probably be checked at each prenatal appointment, even though most women in their 20s have only a small risk of hypertension during pregnancy. New research shows that you have about half the risk of gestational diabetes that women in their 40s do, which is why recent guidelines from the American Diabetes Association suggest eliminating the once routine test for gestational diabetes in women age 25 or under.

YOUR EMOTIONAL SELF

How you feel about your pregnancy may depend, in great part, on other things in your life. Some women who postpone job advancement to have a baby feel ambivalent or resentful at first, says Diane Ross Glazer, Ph.D., a psychotherapist in Woodland Hills, CA. "Another concern is body image, which is a bigger issue for most women in their 20s than for those who are older. Also, a woman at this age is likely to be focused more on her marriage than on other parts of her life, such as her job, and adding a third person into the mix may be difficult," says Glazer.

RISKS TO YOUR BABY

The miscarriage rate during these years is about 9.5 percent, the lowest it will ever be. Because your eggs are still relatively young, your baby is much less likely to be born with a birth defect such as Down syndrome (1 in 1,667 births among women age 20) or other chromosomal abnormalities (1 in 526 among women age 20). Yet more infants with these disorders are born to women in their 20s because those in this age group have more babies and women past 35 are more likely to be offered screening tests and may elect to terminate a pregnancy in which the fetus has a birth defect.