Confirmed severe maternal morbidity is associated with high rate of preterm delivery

Abstract

Background: Because severe maternal morbidity (SMM) is increasing in the United States, affecting up to 50,000 women per year, there was a recent call to review all mothers with SMM to better understand their morbidity and improve outcomes. Administrative screening methods for SMM have recently been shown to have low positive predictive value for true SMM after chart review. To ultimately reduce maternal morbidity and mortality we must better understand risk factors, and preventability issues about true SMM such that interventions could be designed to improve care.

Objective: Our objective was to determine risk factors associated with true SMM identified from California delivery admissions, including the relationship between SMM and preterm delivery.

Study design: In this retrospective cohort study, SMM cases were screened for using International Classification of Diseases, Ninth Revision codes for severe illness and procedures, prolonged postpartum length of stay, intensive care unit admission, and transfusion from all deliveries in 16 hospitals from July 2012 through June 2013. Charts of screen-positive cases were reviewed and true SMM diagnosed based on expert panel agreement. Underlying disease diagnosis was determined. Women with true-positive SMM were compared to SMM-negative women for the following variables: maternal age, ethnicity, gestational age at delivery, prior cesarean delivery, and multiple gestation.

Results: In all, 491 women had true SMM and 66,977 women did not have SMM for a 0.7% rate of true SMM. Compared to SMM-negative women, SMM cases were significantly more likely to be age >35 years (33.6 vs 23.8%; P < .0001), be African American (14.1 vs 7.9%; P < .0001), have had a multiple gestation (9.7 vs 2.1%; P < .0001), and, for the multiparous women, have had a prior cesarean delivery (58 vs 30.2%; P < .0001). Preterm delivery was significantly more common in SMM women compared to SMM-negative women (41 vs 8%; P < .0001), including delivery <32 weeks (18 vs 2%; P < .0001). The most common underlying disease was obstetric hemorrhage (42%) followed by hypertensive disorders (20%) and placental hemorrhage (14%). Only 1.6% of women with SMM had cardiovascular disease as the underlying disease category.

Conclusion: An extremely high proportion of women with severe morbidity (42.5%) delivered preterm with 17.8% delivering <32 weeks, which underscores the importance of access to appropriate-level care for mothers with SMM and their newborns. Further, the extremely high rate of preterm delivery (75%) in women with placental hemorrhage in combination with their 63% prior cesarean delivery rate highlights another risk of prior cesarean delivery: subsequent preterm delivery. These data provide a reminder that a cesarean delivery could be a contributing factor to not only hemorrhage-related SMM, but also to increased subsequent preterm delivery, more reason to continue national efforts to safely reduce initial cesarean deliveries.

Keywords: maternal mortality; preterm delivery; prior cesarean delivery; screening for severe maternal morbidity.