A simple treatment - a hormone-containing vaginal gel - significantly reduces premature births among pregnant women who are at high risk because of a problem with the cervix, government researchers reported Wednesday.

Many factors can lead to premature birth, but Wednesday’s study targets one subset: the thousands of women who develop an unusually shortened cervix, the gateway to the uterus. The findings may prompt more doctors to begin routinely measuring cervical length, using an easy and fairly inexpensive ultrasound scan, midway through pregnancy.

“There will never be ‘the’ solution to preterm birth,” cautions lead researcher Dr. Roberto Romero of the National Institutes of Health. “There will be multiple solutions, and we believe this is one important solution.”

This treatment is not related to an injection called Makena, a synthetic hormone that is controversial because of its high price tag. That drug is aimed at women who’ve already had one preemie and now are pregnant again.

But women may have a short cervix during any pregnancy, and the question was whether applying a gel form of natural progesterone - known as Prochieve - directly onto the problem area could stave off an early delivery.

It worked, cutting by nearly half the rate of particularly early preterm births, those before 33 weeks of gestation who are at particular risk for death or long-term health problems, concluded Romero, who led the study at 44 medical centers around the world.

The study was a collaboration between NIH and Prochieve maker Columbia Laboratories Inc. of Livingston, N.J., which plans to seek Food and Drug Administration approval for the drug for women with short cervix.

“This is very good news, and very timely,” said Dr. John Larsen of George Washington University, a spokesman for the American College of Obstetricians and Gynecologists who wasn’t involved with the research. “People have been using vaginal progesterone for a while, and it’s not been in the high-priced stratosphere.”

Although the company didn’t address price, vaginal progesterone already is sold to treat different conditions, for roughly $20 for a day’s dose.

It makes sense that a vaginal gel would work because “you’re giving it right to the area you want to affect,” added Dr. Alan Fleischman, medical director of the March of Dimes.

The cervix naturally shortens as pregnancy progresses, but at issue here is one about half its usual length during the second trimester. How many women develop that? The study screened 32,000 otherwise healthy pregnant women and found 2.3 percent did, which Fleischman said would equate to about 100,000 U.S. women in a year.

In the new study, 458 women with a short cervix were given either the progesterone gel or a dummy version in a tampon-like applicator, to use daily starting in the second trimester.

Sixteen percent of the women given the dummy gel gave birth before 33 weeks, compared with 9 percent who received the drug, researchers reported in the journal Ultrasound in Obstetrics & Gynecology.

Infants born to the progesterone users were healthier, too, with less respiratory distress and higher birth weights. The women experienced no significant side effects.

Treating 14 women with a short cervix prevented one preterm birth, comparable to or better than some other well-accepted obstetric treatments, the researchers said.

A standard pregnancy ultrasound exam can give a clue about a cervical abnormality but a good measurement requires a transvaginal ultrasound exam, common with standard equipment, said Romero. He wants them to become routine in pregnancy - also valuable, he says, for reassuring women who aren’t at risk.

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By LAURAN NEERGAARD, AP Medical Writer