The cities where women are most likely to have premature babies

Less than one in ten babies was born preterm in the U.S. in 2014, but the rate is nearly twice that high in some cities. A new report card released by the March of Dimes grades the 100 largest U.S. cities based on how many mothers living there give birth before 37 weeks of pregnancy, which can lead to serious health complications for babies.

The preterm birth rate in 2013, the latest year with local data, ranges from 7.2 percent in Portland, Ore., to 18.8 percent in Shreveport, La. (See full list below.)

Dr. Siobhan Dolan, an obstetrician at Montefiore Medical Center in New York and a March of Dimes medical adviser, said the cause of preterm births isn’t the same everywhere, so focusing on local rates can help doctors, parents and researchers prevent them. “For example, smoking has a bad effect on health for everyone and pregnant women in particular," Dolan said. "There’s parts of the country where 20 percent of pregnant women still smoke."

Still, she said that "there’s not one simple answer, there’s not one pill or one shot that will make the difference,” Dolan said.

The national preterm birth rate spiked in the mid-2000s. Dolan said a number of initiatives have contributed to the decline, including new guidelines that recommend doctors only implant one embryo in at a time during an in-vitro fertilization cycle; doctors discouraging early elective delivery; better access to pre-natal care thanks to the Affordable Care Act; and making sure women have access to birth control to space births the ideal 18 months apart.

Dolan added, “in about half of cases of preterm birth, there’s no identified ‘cause’, quote unquote. We need more research to provide insight into why some women deliver preterm.” She said researchers are not sure why women of some races are more likely to deliver preterm babies."

List of cities by premature birth rate in 2013