CLEARWATER, Fla. — Heather Winfield was eight months into her second pregnancy when she discovered that she had gestational diabetes, putting her and her developing baby at risk for serious health problems.

“You feel incredibly guilty because you feel like you did something wrong,” said Winfield, 38, who works in development at Eckerd College in St. Petersburg, Fla.

In fact, she and her doctor did many things right to address what’s becoming a more common condition.

When an initial test wasn’t conclusive, her doctor ordered another that diagnosed the condition. And Winfield took swift action, changing her diet and increasing her exercise to get her blood sugar under control before the birth.

But according to a new study, too often expectant mothers are not screened for diabetes, with potentially dangerous consequences during and after pregnancy.

Though experts say all pregnant women should be screened for diabetes, nearly a third of the more than 900,000 women studied were not, according to the report in Obstetrics and Gynecology. one in five who did develop gestational diabetes did not get a follow-up screening after giving birth, even though more than half of such women go on to develop Type 2 diabetes.

If not properly managed, gestational diabetes can lead to high blood pressure or preeclampsia, premature delivery and babies weighing 9 pounds or more, which makes a cesarean section more likely. Longer-term, the condition, if not treated, can double the risk that the child will become obese and will have an increased chance of developing diabetes.

“It’s a significant problem, and I am seeing more of it now,” says Dr. Brooke Ritter, an ob-gyn at Morton Plant Hospital in Clearwater, who diagnosed Winfield’s diabetes. The American Diabetes Association estimates that 4 percent of pregnant women — about 135,000 annually — develop the condition, but Ritter is among those who think the incidence may be as high as 10 percent.

Ritter and other experts attribute the increase to women putting off pregnancy until later in life, as well as the continuing obesity epidemic.

“There are more obese adult women getting pregnant, so you’re going to see more gestational diabetes,” says Dr. Henry Rodriguez, a professor of pediatrics and clinical director of the University of South Florida Diabetes Center in Tampa. Add a family history of Type 2 diabetes to obesity, and the first result often is a pre-diabetes condition known as insulin resistance, which many people don’t even know they have.

“But add pregnancy to the picture and that may be enough to tip that person into diabetes,” Rodriguez said.

Experts aren’t sure exactly why pregnancy can trigger diabetes. but they do know that certain hormones produced during pregnancy interfere with the production of insulin, the hormone needed to carry glucose from the bloodstream to the cells, which convert it into energy.

As the baby grows, the placenta makes more and more of the insulin-interfering hormones. in most women, the pancreas compensates by producing more insulin. but when that doesn’t happen, blood sugar rises, resulting in gestational diabetes.

The condition, which typically develops in the final trimester, doesn’t usually cause the mother noticeable symptoms. It takes an oral glucose or blood-screening test to detect.

Ritter considers screening for elevated blood sugar a routine part of prenatal care. “We screen everyone,” usually at 24 to 28 weeks’ gestation if the patient is younger than 25 and has no risk factors, she said. but those who are older, overweight or have a family history of diabetes should be screened earlier, “perhaps at their first prenatal visit if they are at highest risk.”

Rodriguez says women who don’t get proper prenatal care are most likely to miss out on screening and go undiagnosed.

As Winfield discovered, most gestational diabetes can be well managed, usually without medication.

When Winfield was diagnosed in December, she met right away with diabetes nurse educators. they helped change her eating habits — no more fast food and no more skipping meals — and started her on a specific, planned activity program.

“I learned that chasing after a 2-year-old doesn’t count,” she says. Those simple steps brought her blood sugar under control and she lost 10 pounds, something her doctor approved and monitored closely. Bonus: She says she had so much more energy, “I could go another nine months if I had to.”

But baby Jonah arrived about two weeks early, on Jan. 12, weighing a healthy 7 ½ pounds.

Women at greater risk for developing diabetes during pregnancy often:

— are 25 or older

— are obese (BMI greater than 30)

— Have pre-diabetes (insulin resistance) before pregnancy

— Have a parent or sibling with Type 2 diabetes

— had gestational diabetes in a previous pregnancy

— Delivered a baby weighing more than 9 pounds

— had an unexplained stillbirth

— are black, Hispanic, American Indian or Asian

Risks to the baby:

— Excessive size may mean a C-section.

— Breathing problems at birth

— Low blood sugar at birth

— Jaundice at birth

— Type 2 diabetes later in life

— Obesity later in life

Risks to the mother:

— High blood pressure (preeclampsia) during pregnancy

— C-section delivery

— Future Type 2 diabetes

Sources: American Diabetes Association; Mayo Clinic