First-time mom Jill Teeters did everything she was supposed to in order to have a healthy pregnancy. She ate well, took her vitamins and regularly saw her doctor. The weeks ticked by, and everything seemed to progress normally.
Then one fall day, Teeters, who was 37 at the time, woke up feeling off -- a sense she chalked up to entering her third trimester. By the next day, however, she began feeling really unwell and called her doctor who examined her and sent her home to rest. That night, she called her OB-GYN again after she continued to feel very uncomfortable, and then drove to the hospital to get checked. This time, her doctor told her she should not plan on leaving. Teeters -- who was three months from her due date -- would have to stay on bed rest until her baby was born. Instead, her water broke that night and in under 27 minutes, Teeters' son, Aidan, was delivered via emergency C-section. She had been pregnant for just 28 weeks and five days, and her baby boy weighed just 3 pounds.
"I was completely healthy. I had no risk factors," said Teeters, who is the 2014 ambassador for the nonprofit March of Dimes. "There was no reason that this shouldn't have been just your kind of average, everyday, 40-week gestation and delivery."
"I was completely healthy. I had no risk factors."
Each year, roughly 1 in every 9 babies born in the United States is born preterm, or before 37 weeks, putting them at risk for a host of short- and long-term health problems -- and even death. Costs associated with premature birth in the United States now exceed $26 billion annually, and while the national rate has steadily declined since its peak in 2006, a significant percentage of preterm births, like Teeters', remain unexplained.
A new review, published in the journal Science this month, argues that in order to truly get a handle on what causes preterm birth, and do a better job of preventing it, doctors and researchers must transition away from thinking of it simply as one condition -- labor that happens before a woman reaches 40 weeks -- to a complex syndrome with many causes.
"We have been thinking of preterm birth as though it is one condition, and this is not the right way of thinking about the problem," Dr. Roberto Romero, chief of the perinatology research branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, told The Huffington Post.
Romero, an author of the paper, drew a comparison to a middle-aged man who arrives at the emergency room with a bad cough. That cough could have any number of causes -- a cold, pneumonia, even cancer. Likewise, premature labor represents a collection of signs and symptoms caused by what he called multiple "disease processes."
"The challenge ahead," Romero continued, "is to figure out which is the mechanism operating in each patient. We need to identify early biomarkers before women present with preterm labor."
"We need to identify early biomarkers before women present with preterm labor."
The review draws attention to several potential causes of preterm labor. Estimates suggest, for example, that 1 in every 4 premature babies is born to a woman with a silent infection within the amniotic sac, which is only detected when the membranes rupture and labor contractions begin. Microorganisms in the vaginas of pregnant women can and often do change, but experts do not yet know why bacteria gain access to the amniotic fluid in some cases, but not others.
"Why do some women get an ascending infection, while most women do not?" Romero asked. "We are very interested in determining, 'Who are the women who are at risk for developing [the high-risk] infection?'"
Other women have no infection, but instead experience inadequate blood supply to the placenta that may be the result of certain key arteries failing to expand sufficiently during pregnancy.
"We've known for a long time that the influences are heterogeneous, and that's why you have to consider all of these different approaches," said Dr. Louis Muglia, director of the Center for Prevention of Preterm Birth at Cincinnati Children's Hospital Medical Center.
"There are people who are very committed to working in this area that have been channeling their thoughts in a very targeted way, in a pathway that has been, perhaps, established for a longer time," he added. "This [paper] introduces new concepts for them to think about."
Both Romero himself and the new review emphasized that recent research has uncovered relatively new and well-established risk factors for preterm birth, such as cervical length. Women with a short cervix may benefit from vaginal progesterone treatment, a hormone that can help prevent preterm birth. Women who have already had one preterm birth may also benefit from progesterone shots in subsequent pregnancies.
"The preterm birth rate [in the United States] has declined for the last seven years, and for decades it was going up and up and up," said Dr. Scott Berns, senior vice president and deputy medical officer with the March of Dimes. "The authors do point out the fact that we've done quite a bit around identifying risk factors and in areas around prevention." The March of Dimes has campaigned against the use of labor induction before 39 weeks that isn't medically necessary, and has worked to spread knowledge about risky, modifiable behaviors, such as smoking during pregnancy and poor nutrition.
"[But] the reality is that even if we implemented all the things we know can help reduce preterm birth, there's much more work to do," Berns said. "We're not going to continue to drop the rates without discovery research."
"We're not going to continue to drop the rates without discovery research."
In the meantime, that means thousands of mothers, such as Teeters, are forced to sit with more questions than answers about why their children were born so early and what, if anything, they could have done to prevent it. After 49 days in the neonatal intensive care unit, Aidan went home with his parents for the first time, and is now a perfectly healthy 6-year-old who is about to enter the first grade. But the experience affected the choices Teeters and her husband made regarding future children.
"There was no infection. There was no pre-existing condition. There was nothing they could point to as the trigger. It just happened, and that's scary," Teeters said. Her doctors warned that if she were to conceive again, she would be considered high-risk and likely put on bed rest very early in her pregnancy.
"We don't know what caused it," Teeters said, "And there's no guarantee that we'd be as lucky the next time as we were before."
When Aidan was born, he was so small Teeters' husband's wedding ring fit comfortably around his wrist.