The rapidly rising rate of maternal mortality in the United States may be in part related to recent changes in data collection and statistical modeling for death during or after pregnancy, according to a new study published Wednesday in the American Journal of Obstetrics and Gynecology.

Researchers argue that the discrepancy may be due to the recording of deaths of women who coincidentally were pregnant as deaths caused by pregnancy itself. Their findings suggest that maternal mortality is largely stable and that deaths due to obstetric complications have decreased in recent years.