Association of Severe Maternal Morbidity With Subsequent Birth

Abstract

Importance: Women who experience severe maternal morbidity (SMM) might have lasting health issues, and the association of SMM with the probability of future reproductive intentions is unknown.

Objective: To examine the association between SMM in a first birth and the probability of a subsequent birth.

Design, setting, and participants: Retrospective, population-based cohort study conducted among 1 046 974 women in Sweden who had their first birth between 1999 and 2021.

Exposure: Overall SMM and SMM subtypes were identified among all deliveries at 22 weeks of gestation or later (including complications within 42 days of delivery) from the Swedish Medical Birth Register and National Patient Register.

Main outcomes and measures: All women with a recorded first delivery were followed up from 43 days postpartum until the first day of the last menstrual period of the second pregnancy that resulted in a birth (stillbirth or live birth) or until death, emigration, or end of follow-up on December 31, 2021. Multivariable Cox proportional hazards regression was used to estimate associations between SMM and time to subsequent birth with adjusted hazard ratios (aHRs). Sibling analysis was performed to evaluate potential genetic and familial confounding.

Results: A total of 36 790 women (3.5%) experienced an SMM condition in their first birth. Women with any SMM had a lower incidence rate of subsequent birth compared with those without SMM in their first delivery (136.6 vs 182.4 per 1000 person-years), with an aHR of 0.88 (95% CI, 0.87-0.89). The probability of subsequent birth was substantially lower among women with severe uterine rupture (aHR, 0.48; 95% CI, 0.27-0.85), cardiac complications (aHR, 0.49; 95% CI, 0.41-0.58), cerebrovascular accident (aHR, 0.60; 95% CI, 0.50-0.73), and severe mental health conditions (aHR, 0.48; 95% CI, 0.44-0.53) in their first birth. The associations were not influenced by familial confounding as indicated by sibling analyses.

Conclusions and relevance: Our findings suggest that women who experience SMM in their first birth are less likely to have a subsequent birth. Adequate reproductive counseling and enhancing antenatal care are crucial for women with a history of SMM.

Figure 1.. Development of the Study Cohort

Figure 2.. Kaplan-Meier Cumulative Incidence Rates of Subsequent Birth Among Women With and Without Severe Maternal Morbidity in Their First Birth

Follow-up time is truncated at 10 years. Median follow-up time for women with severe maternal morbidity was 2.37 (IQR, 1.32-5.36) years and for those without severe maternal morbidity was 2.05 (IQR, 1.17-3.97) years. Shading indicates 95% CI.

Figure 3.. Hazard Ratios for Subsequent Birth Among Women With SMM and Specific SMM Types at the Time of Their First Birth, Sweden, 1999-2021

HELLP indicates hemolysis, elevated liver enzymes, and low platelet count; HR, hazard ratio; and SMM, severe maternal morbidity. ^aEstimates are adjusted for maternal age, educational level, maternal height, body mass index, multiple birth, smoking, use of assisted reproductive technology, cohabitation with a partner, country of birth, calendar year of birth, and pregestational diabetes and hypertension prior to first delivery. ^bNo SMM was the reference group for the primary exposure (composite SMM) and its subtypes. ^cSMM was defined based on diagnostic and procedure codes in hospital records between 22 weeks of gestation and 42 days postdelivery from the Swedish Medical Birth Register and National Patient Register (for specific codes, see eTable 1 in Supplement 1). ^dOther types include sickle cell anemia with crisis, acute and subacute liver failure, acute respiratory distress syndrome, and status epilepticus.

Figure 4.. Sibling Analysis Among Women With SMM and Their Full Sisters Without SMM the Time of Their First Birth Using Stratified Cox Regression Models, Sweden, 1999-2021

HELLP indicates hemolysis, elevated liver enzymes, and low platelet count; HR, hazard ratio; and SMM, severe maternal morbidity. ^aEstimates are adjusted for maternal age, educational level, maternal height, body mass index, multiple birth, smoking, use of assisted reproductive technology, cohabitation with a partner, country of birth, calendar year of birth, and pregestational diabetes and hypertension prior to the first delivery. ^bNo SMM was the reference group for the primary exposure (composite SMM) and its subtypes. ^cSMM was defined based on diagnostic and procedure codes in hospital records between 22 weeks of gestation and 42 days postdelivery from the Swedish Medical Birth Register and National Patient Register (for specific codes, see eTable 1 in Supplement 1). ^dOther types include sickle cell anemia with crisis, acute and subacute liver failure, acute respiratory distress syndrome, and status epilepticus.