The Society of Professional Journalists announced today that “Lost Mothers,” a project with NPR, has won the Sigma Delta Chi Award for excellence in journalism. The collaboration illuminated a disquieting trend: The United States, which spends more per capita on health care than any other country, has the highest rate of maternal mortality and severe morbidity in the affluent world.

ProPublica reporters Nina Martin, Adriana Gallardo and Annie Waldman, along with NPR special correspondent Renee Montagne, explored the myriad reasons behind this crisis.

The comprehensive project included an intimate narrative about Lauren Bloomstein, a neonatal nurse who died in childbirth in the hospital where she worked. Bloomstein died because her preeclampsia, a type of high blood pressure that only occurs in pregnancy or postpartum, wasn’t diagnosed in time. Her story reflects a health care system with no standard protocol for what to do in obstetric emergencies, and one with a greater emphasis on the baby’s health than on the mother’s.

Another piece explored African-American women’s disproportionate rates of maternal mortality, focusing on the experience of Shalon Irving, a CDC researcher who studied racial health disparities. She died three weeks after giving birth. The feature explored how stress from social inequalities, as well as unconscious biases throughout the medical system, can lead to poor maternal outcomes for black women. Reporters also used patient discharge data to document racial disparities at the hospital level.

The series has had significant impact. Citing “Lost Mothers,” state and local lawmakers around the country have adopted a flurry of bills aimed at reforming how maternal deaths are identified and investigated. Indiana and Oregon passed laws creating maternal mortality review committees to scrutinize deaths and near-deaths among expectant and new mothers, and to make policy recommendations to improve maternal health. Similar bills are pending in Washington, D.C., Pennsylvania, Connecticut, Maryland and New Jersey.

See a list of all this year’s Sigma Delta Chi Award winners.