KALAMAZOO, Mich. – The U.S. Centers for Disease Control and Prevention estimates that 12 percent of all pregnancies in this country end in premature birth.

That’s one in eight babies, or about half a million, born early and at risk of serious health problems.

In June, the National Institutes of Health for the Office of the Surgeon General convened a conference in Maryland to look at the issue of preterm births – in particular late preterm births.

Conference participants discussed the possibility that unnecessary Caesarean sections may – at least in part – be fueling the problem.

Full-term pregnancy generally lasts between 38 and 42 weeks. Preterm births are considered anything under 37 weeks of gestation. Late preterm births are those falling between 34 and 36 weeks.

Late preterm birth

Preterm births have risen 20 percent since 1990, according to the March of Dimes.

“We attribute the majority of that increase to late preterm births,” said Kara Hamilton, state director of program services for the March of Dimes for Michigan.

A new study on preterm births from the CDC and the March of Dimes confirms that trend.

Although the public perception is that those late preterm babies do not suffer ill effects from falling just a few weeks short of full gestation, that is not the case, Hamilton said.

“During the late preterm phase, the brain develops quite significantly,” she said. “A baby’s brain at 35 weeks weighs two-thirds of what it will weigh at 40 weeks.”

While it is true that the longer a baby remains in utero the better its changes of survival, late preterm babies face some of the same risks that early-preterm babies do, Hamilton said. They can have difficulty coordinating suckling, swallowing and breathing, are more likely to have general breathing problems, and are more likely to die of Sudden Infant Death Syndrome.

Unknown causes

Part of the difficulty in remedying the problem is that physicians simply do not know all the causes of preterm birth.

“For over 50 percent of women who go into preterm labor, there is no known cause,” Hamilton said. “They are taking their vitamins, eating right, not smoking or drinking.”

Dr. Catherine Schauer, an obstetrician and gynecologist with Borgess Women’s Health, said genetics appear to play at least some part in the situation. Women who have previous preterm births are at greater risk of delivering early in subsequent pregnancies.

Other things that physicians definitely know affect early deliver are stress, being either extremely young or old at the time of pregnancy, and carrying multiple fetuses. The rise in multiple births has affected the numbers of preterm births as well.

But Hamilton noted that the medical community also has observed increased preterm births in recent years among women carrying single babies.

C-sections

The CDC and March of Dimes study indicated a link between C-sections and preterm births. Over the past nine years, there have been increases in both C-sections and singleton births.

Some women and their doctors schedule C-sections for convenience or other personal reasons, Hamilton said.

“The data still needs to be teased to know how many of these C-sections are elective or have medical reasons,” she said. “But we have seen an alarming increase in C-sections.”

Reducing risk

While researchers continue to search for the causes of preterm births, there are steps that expecting mothers can take to reduce their risk of giving birth early:

• Make appointments for your prenatal visits and keep them.

• Take your prenatal vitamins.

• If you smoke, stop. The same for illegal drugs.

• Work with your doctor to monitor and control chronic health issues such as diabetes and hypertension.

• Know the warning signs of preterm labor, such as spotting, backaches, spikes in temperature and leaking fluids. And contact your doctor if you experience any of them.

• Find ways to relax and reduce stress.