Two years ago when Mary Donovan found out she was pregnant, she never considered going anywhere but Jackson Memorial Hospital to have her baby.

Sure, the accommodations at the sprawling campus near downtown Miami don’t offer the ambience of the hotel-like rooms at some hospitals. But she thought Jackson offered something better: specialists and one of the best neonatology units in the country.

At 41, Donovan was among the growing number of women falling into the category of high-risk pregnancy. As more women have babies later in life, more have multiple births and more suffer from obesity, the number of pregnancies considered high risk has ticked up. In 2007, the number of preterm babies born before 37 weeks reached one in every eight, higher than any year between 1981 and 2002, according to the Centers for Disease Control and Prevention.

And that has driven up the need for hospitals like Jackson where “we created multiple layers of specialists and sub-specialists who can take care of things in the blink of an eye,” said Dr. Salih Yasin, vice chair of obstetrics and gynecology and director of obstetrics and patient safety for the Women’s Hospital Center at Jackson Memorial Hospital.

For Donovan, a radiology nurse at Miami Children’s Hospital, getting pregnant capped a harrowing few years. In 2007, she was still single but determined to have a baby. Then came a big surprise.

“My goal in 2007 was, all I wanted was to be a mom. People said, ‘But you’re still single,’ and I said ‘I don’t care. I’ll get in vitro if I have to.’ Then I got my diagnosis [of thyroid cancer] and they said you can’t get pregnant for a year after treatment. I thought, ‘oh my God, that’s like getting a hysterectomy.’ ”

The cancer diagnosis prompted Donovan, a Buddhist who lives in Fort Lauderdale, to do some soul searching. She decided it was time to start meeting more people and living life a little larger, so she joined a social network. Exactly one year after her treatment, she met a man, who became her partner. One year later, she was pregnant.

For Donovan, age and cancer were not her only concerns. She also suffered from migraines and had learned during treatment that she had a gene mutation that made her prone to miscarriage. While she had never had a miscarriage, her obstetrician at Jackson, Dr. Rabah Laoun, wanted her on blood thinners. So for the next nine months, Donovan gave herself daily injections and made frequent visits to her doctor.

Last year, U.S. News ranked Holtz Children’s Hospital at Jackson Memorial No. 25 in the nation among pediatric hospitals. The hospital overall ranked No. 1 when the field narrowed to hospitals in South Florida.

Despite the growing number of high-risk pregnancies, the news is not all bad if you look closely at what drives it: older women now able to have children and successful fertility treatments. Both can produce more twins and other multiples.

“When I came to Miami in 1984, national data told us women having babies after 35 was around nine to 11 percent. Nowadays, it’s 27 to 30 percent,” Yasin said.

Advances in medicine have also enabled doctors to diagnose problems earlier, he explained.

“People are more alert, more aware at an earlier stage. It gives the impression that there is more risk in pregnancy,” he said.