Severe maternal morbidity from pregnancy through 1 year postpartum

Few recent studies have examined the rate of severe maternal morbidity occurring during the antenatal and/or postpartum period to 42 days after delivery. However, little is known about the rate of severe maternal morbidity occurring beyond 42 days after delivery.

This study aimed to examine the distribution of severe maternal morbidity and its indicators during antenatal, delivery, and postpartum hospitalizations to 365 days after delivery and to estimate the increase in severe maternal morbidity rate and its indicators after accounting for antenatal and postpartum severe maternal morbidity to 365 days after delivery.

This was a retrospective cohort study using birth and fetal death certificate data linked to hospital discharge records from Michigan, Oregon, and South Carolina from 2008 to 2020. This study examined the distribution of severe maternal morbidity, nontransfusion severe maternal morbidity, and severe maternal morbidity indicators during antenatal, delivery, and postpartum hospitalizations to 365 days after delivery. Subsequently, this study examined "severe maternal morbidity cases added," which represent cases among unique individuals that are included by considering the antenatal and postpartum periods but that would be missed if only the delivery hospitalization cases were included.

A total of 64,661 (2.5%) individuals experienced severe maternal morbidity, whereas 37,112 (1.4%) individuals experienced nontransfusion severe maternal morbidity during antenatal, delivery, and/or postpartum hospitalization. A total of 31% of severe maternal morbidity cases were added after accounting for severe maternal morbidity occurring during the antenatal or postpartum hospitalization to 365 days after delivery, whereas 49% of nontransfusion severe maternal morbidity cases were added after accounting for nontransfusion severe maternal morbidity occurring during the antenatal or postpartum periods. Severe maternal morbidity occurring between 43 and 365 days after delivery contributed to 12% of all severe maternal morbidity cases, whereas nontransfusion severe maternal morbidity occurring between 43 and 365 days after delivery contributed to 19% of all nontransfusion severe maternal morbidity cases.

Our study showed that a total of 31% of severe maternal morbidity and 49% of nontransfusion severe maternal morbidity cases were added after accounting for severe maternal morbidity occurring during the antenatal or postpartum hospitalization to 365 days after delivery. Our findings highlight the importance of expanding the severe maternal morbidity definition beyond the delivery hospitalization to better capture the full period of increased risk, identify contributing factors, and design strategies to mitigate this risk. Only then can we improve outcomes for mothers and subsequently the quality of life of their infants.