Hormone injections may help women carry their babies to full term.
Studies show that women with a history of preterm births are 30 percent to 40 percent more likely to have the same problem with later pregnancies.
Doctors normally offer medication or advise women to rest to help reduce the possibility of a preterm birth.
Doctors said hormone injections are giving hope to pregnant women.
Kasie and McKenzie Bowman look a lot alike, but their births were significantly different.
Kasie was born six weeks early.
"She ended up staying in the hospital about a week with pneumonia," said Kasie's mother, Jamie Bowman.
Bowman decided to take part in a study at the
University of North Carolina
during her third pregnancy.
Bowman and hundreds of other women received injections of the hormone progesterone every week for 16 weeks.
"It's a painful injection and particularly if you're thin. You're going to have a sore bottom from it," Dr. John Thorp, a gynecologist at UNC.
Although painful, Thorp said the shots had a tremendous effect.
The injections reduced the risk of preterm birth before 37 weeks by 34 percent. The risk of delivering earlier than 32 weeks dropped 42 percent.
"This made a big difference," said Bowman, who carried McKenzie to fullterm and even was induced because of the baby's size.
"She actually ended up weighing 10 pounds 11 and a quarter ounces. So, she was a big baby," Bowman said.
Thorp said doctors are not completely sure how the hormone works.
"The simplest theory would be that there's some sort of progesterone deficiency and you're making up for low progesterone levels," he said.
Bowman said she is just happy her daughter is healthy and hopes it helps other couples become parents.
"There are so many women that can't carry babies at all and have trouble with miscarriages. So I hope it will encourage them to do something," she said.
Progesterone was used in the 1960s and '70s, but researchers stopped using it when other hormone-based treatments were proven to cause birth defects.
Thorp said the UNC study proved the safety of progesterone injections.
Progesterone is FDA-approved but no drug company in the United States currently sells it.
Progesterone injections are also not widely available yet.
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