ATLANTA, Georgia (CNN) -- Kelli Heath just turned 30 and she's spending more and more time deflecting questions from family and friends about when she plans to get pregnant.
Scott and Kelli Heath, married two years, are delaying having children so they can have "us" time.
"A lot of women have timelines," Heath said. "I don't."
Heath, a full-time event planner in Atlanta, Georgia, married her husband, Scott, two years ago. They want to have children one day, but not right away. "Our priority as a couple is 'us' right now," she said.
More and more couples like the Heaths are waiting to expand their families until the woman is well into her 30s or older. Work, travel and the desire to save money are some of the reasons cited for the delay in having a baby.
Obstetrician and gynecologist Michael Randell cautioned that such delays may come with consequences. "There is a lot of anxiety among patients," Randell said. "I have 20-year-olds coming to me concerned whether or not they can get pregnant."
In reality, experts say, women over 35 struggle the most to get pregnant. As a woman ages, the quality of her eggs tends to decline and she may not ovulate as frequently.
"Statistics are against you," Randell said. "You only have a 15 percent chance of conceiving each month. About 85 percent of people will conceive in the first year of trying."
"The reason why it is more difficult to get pregnant these days is more people are waiting longer."
He also blamed monthly timing. "It's one of the most shocking things that I see, when patients really don't know that they only have a small window of opportunity to get pregnant each month. The optimal time of the month for ovulation is 14 days after the first day of your last menstrual period."
Randell tells his patients that certain lifestyle changes may help improve a woman's fertility and get her body ready long before she is prepared to get pregnant.
"If you're smoking, that can affect fertility both for the male and female; so can using drugs," he said.
The American College of Obstetricians and Gynecologists suggests trying to lose weight if you are overweight or obese, eating a healthy diet and exercising regularly.
Taking a folic acid supplement before conception is important to prevent birth defects. Health Minute: Watch more on having a healthy pregnancy »
Check to make sure your immunizations are up to date to lower the risk of infection while pregnant.
Finally, Randell recommends couples relax and give it some time. "If you haven't been successful in 12 months of trying, then it is time to seek help," he said.
The problem, he noted: "No one wants to wait 12 months. Most patients are asking for testing at three months."
Randell starts by taking a woman's menstrual history. He then performs basic testing to determine whether a woman is ovulating properly. A blood test measures the amount of hormones in the blood. X-rays will be taken to see whether the woman's fallopian tubes are open. The male partner would be checked for an abnormal sperm count.
If ovulation is not occurring in the woman, then doctors will start investigating whether there is a medical reason and how to solve it. Randell said one of the most common problems he sees involves an improperly working thyroid gland.
Randell explained another step may be to prescribe a fertility drug such as Clomid, which stimulates ovulation. If that doesn't work, Randell will refer the couple to an infertility doctor called a reproductive endocrinologist.
Now that she's 30, Heath knows she's in the prime of her reproductive years. Rather than fret over a ticking biological clock and potential complications she said, "We'll cross that bridge when we get there." E-mail to a friend
Judy Fortin is a correspondent with CNN Medical News.