AUSTIN, Texas -- The number of women having babies over age 35 has been rising steadily. The problem is a woman's fertility starts to decrease at age 32.

Doctors say a relatively new blood test can help a woman determine the health and number of her eggs.

The anti-mullerian hormone test is offered at fertility clinics and OB/GYN offices.

Sarah Kuykendall tried it and now has healthy twin baby girls - Eden and Emory.

“We decided after about two years of marriage we wanted to start a family,” said Sarah Kuykendall. “Naïve as we were we thought as we made that agreement that we wouldn't have that much trouble."

Three miscarriages later, Sarah wanted to know what was wrong.

"We kind of wanted to see if there was a problem,” she said. “If it was me physically or if it was something like egg reserve."

Her fertility specialist, Dr. Natalie Burger at the Texas Fertility Center, recommended the anti-mullerian hormone test.

"The AMH test is a simple blood test that can give you an idea as to your relative egg count, and it's something you can actually get easily done with your primary care provider, (and/or) your OB/GYN,” said Dr. Burger.

“It's actually something that can be done on any day of the menstrual cycle or even on the birth control pill."

It works by measuring the anti-mullerian hormone that surrounds a woman's ripe eggs.

"And so the fewer that you have in your ovaries as time goes on, the less of the hormone you have,” Dr. Burger said.

She adds that more women are taking the test because more research has been done and doctors are able to better understand the results.

Sarah took it – and discovered her count was low.

"I think at that time I was 32,” said Kuykendall. “In my mind, I was thinking that I was a little young for that result."

Despite the disappointment, Doctor Burger encouraged her – and recommended intrauterine insemination and later, in vitro fertilization, which after 5 years, gave her the greatest gift.

"We're just incredibly happy and so thankful," said Kuykendall.

Doctors said the test is usually covered by insurance, but if you pay out of pocket, it is about $140.