Defining severe maternal morbidity-When is it time to stop?

Re-exploration following caesarean birth: a prospective national case-control study using the United Kingdom Obstetric Surveillance System (UKOSS) data collection system

BACKGROUND

Re-exploration following caesarean birth and the associated maternal morbidity has not been investigated in the UK. Our aims were to determine the national incidence and identify the associated risk factors.

METHODS

We conducted a prospective observational case-control study across 194 UK consultant-led maternity units in women whose caesarean birth was complicated by a re-exploration. Independent factors for re-exploration were analysed using multivariable multi-level mixed effects logistic regression.

RESULTS

Over the study period (1 June 2021 and 31 May 2022) 238,423 caesarean births were recorded across the UK of which 187 women underwent re-exploration, giving an incidence of one re-exploration per 1282 caesarean births (95%CI 1:1099-1:1471). Haemorrhage (124/187, 66.3%) and sepsis (31/187, 16.6%) were the most common findings at re-exploration. Median (IQR [range]) time interval to re-exploration following the caesarean birth was 1 (0-4 [0-28]) day. Mechanical ventilation was required in 34 (18.6%) women, cardiac arrest was reported in 5 (2.7%) and 3 (1.6%) women died. Independent preceding factors associated with a re-exploration included: receipt of blood transfusion (adjusted OR (95%CI) 8.25 (2.66-25.61)); use of a general anaesthetic (adjusted OR (95%CI) 3.33 (1.61-6.88)); pre-eclampsia (adjusted OR (95%CI) 3.27 (1.55-6.91)); black ethnicity (adjusted OR (95%CI) 3.14 (1.39-7.11)); postpartum haemorrhage (adjusted OR (95%CI) 2.82 (1.81-4.37)); use of anticoagulants or antiplatelet drugs pre-caesarean birth (adjusted OR (95%CI) 2.26 (1.35-3.81)); and emergency caesarean birth (adjusted OR (95%CI) 1.89 (1.01-3.57)).

CONCLUSION

Re-exploration following caesarean birth in the UK is uncommon but is associated with significant maternal morbidity and mortality. These study findings will help guide informed consent and encourage appropriate surveillance of high-risk women postpartum.

Severe Maternal Morbidity: A Comparison of Definitions and Data Sources

Severe maternal morbidity (SMM) is a composite outcome measure that indicates serious, potentially life-threatening maternal health problems. There is great interest in defining SMM using administrative data for surveillance and research. In the United States, one common way of defining SMM at the population level is an index developed by the Centers for Disease Control and Prevention. Modifications to this index (e.g., exclusion of maternal blood transfusion) have been proposed; some research defines SMM using an index introduced by Bateman et al. (Obstet Gynecol. 2013;122(5):957-965). Birth certificate data are also increasingly being used to define SMM. We compared commonly used US definitions of SMM among all California births (2007-2012) using the kappa (κ) statistic and other measures. We also evaluated agreement between maternal morbidity fields on the birth certificate as compared with health insurance claims data. Concordance between the 7 definitions of SMM analyzed was generally low (i.e., κ < 0.41 for 13 of 21 two-way comparisons). Low concordance was particularly driven by the presence/absence of transfusion and claims data versus birth certificate definitions. Low agreement between administrative data-based definitions of SMM highlights that results can be expected to differ between them. Further research on validity of SMM definitions, using more fine-grained data sources, is needed.