"We didn't marry until I was 38," Harper says, "and we always knew we didn't have a lot of time to waste."
Like many women who marry later in life, Harper didn't think much about her fertility until she'd reached the age at which many doctors warn that healthy pregnancies don't come easily.
"What a lot of women do not know is that we are born with all of the eggs that we are going to get. And a lot of those eggs are used before we get out of puberty," says Kim Hahn, founder and CEO of Conceive magazine. "We are not like men; we do not regenerate eggs."
Concern about her age prompted Dawn Crowley's doctors to encourage her to get pregnant even before her planned marriage.
"When I told my doctor we wanted to have children after we married, she looked at me and said, 'I understand the need to be married, but you're 38 years old. I suggest you try right now,'" recalls Crowley, who is now 40.
The Birmingham, Mich., resident married Jim Crowley, 50, in August 2007. They gave birth to a healthy 7 1/2-pound girl, Kate, six months later.
The statistics might surprise some women:
At 20, the odds of getting pregnant when everything is timed perfectly are about 25 percent per cycle. By age 30, the odds drop to 10 percent to 15 percent each month, and by age 40, it's 5 percent, reports Conceive magazine.
Women who get pregnant between the ages of 35 and 45 face a 20 percent to 35 percent chance of miscarriage, according to the American Pregnancy Association. That's on top of common complications such as high blood pressure and gestational diabetes.
By the time a woman is 43, the risk of having a baby with chromosomal abnormalities such as Down's syndrome rises to 1 in 50, from 1 in 1,500 at age 20, according to pregnancyinfo.net
At age 35, the rate is 1 in 350.
The rate of in-vitro fertilization has increased 17 percent from 2003 to 2007, with the greatest increase seen among women ages 35 to 37, according to the Society for Assisted Reproductive Technology. But age also seems to play a role in the success of the procedure. Younger women - those younger than 35 - have about a 40 percent chance of having a live birth with IVF. By the time a woman is 42, the live birth rate with IVF drops to about 11%.
Children born to older parents are more likely to develop autism. That's especially true for first-born kids, according to a study in the December issue of the American Journal of Epidemiology. Also, a Swedish study in the American Journal of Psychiatry found that children with fathers older than 45 were twice as likely to develop schizophrenia.
The trend of women having babies later in life shows no sign of slowing down. The National Center for Health Statistics reports that the percentage of women giving birth for the first time at age 35 or older has increased eight-fold since 1970 - from 1 percent to 8 percent.
The birth rate among women ages 30 to 34 grew 2 percent from 2006 to 2007. Among women 40 to 44, the birth rate grew 1 percent to 9.5 births per 1,000 women - one of the highest rates ever.
"It makes sense that women are waiting longer to start families - college, careers, not meeting the right person earlier in life," says Dr. Kristen Wuckert, an ob-gyn at Mission Obstetrics and Gynecology in Warren, Mich. Years ago, she says she might have seen an older woman once a week; now it's a daily or twice-a-day occurrence.
"Another reason women wait is because they can. We have a lot more options, albeit expensive ones, to help in getting pregnant. It has also become more the norm than the exception.