ProPublica reporter Nina Martin and NPR special correspondent Renee Montagne won this year’s George Polk Award in Journalism in the medical reporting category, for their “Lost Mothers” series on maternal mortality in the U.S. This marks the sixth Polk Award for ProPublica.

The series, which also included stories by ProPublica's Adriana Gallardo and Annie Waldman, illuminated that the U.S. has the worst rate of maternal deaths in the developed world, and 60 percent of those deaths are preventable. Stories included intimate narratives of mothers who died after failing to receive the most basic care, and data analysis showing why black mothers in the U.S. – no matter what their income and education – die at three to four times the rate of white mothers,

The series landed with significant impact. After its publication, two state legislators in New Jersey introduced a bill to heighten monitoring of maternal deaths and encourage hospitals to adopt life-saving treatment protocols. ProPublica’s database identifying 134 of the as many as 900 U.S. women who died from pregnancy-related causes in 2016 inspired a legislator in Texas to create a similar photo gallery for her state, which has one of the highest maternal death rates in the country. At the time, her bill to reauthorize a state committee that reviews maternal deaths was stalled in the legislature. By personifying the issue, the gallery helped revive and pass the measure.

At the start of the project, ProPublica issued a callout, asking people who knew someone who died or nearly died in pregnancy or childbirth to tell ProPublica their stories. Almost 4,500 readers responded, including 3,862 who said they had almost died themselves. This groundbreaking database allowed families, at last and at a minimum, to have the deaths of their loved ones recognized.

Administered by Long Island University, the Polk Awards honor intrepid and influential work, with a premium placed on original and resourceful investigative reporting. See a list of all of this year’s Polk Award in Journalism winners here.