Severe maternal morbidity following attempted forceps or vacuum birth among individuals with a trial of labour after caesarean birth: A population-based cohort study.

INTRODUCTION

Up to 14% of individuals with a trial of labour after caesarean birth (TOLAC) require an operative vaginal birth (OVB). We evaluated the association between forceps vs vacuum birth and severe maternal morbidity (SMM) among individuals with a TOLAC.

METHODS

This is a population-based cohort study of individuals with one prior caesarean birth who delivered a singleton, cephalic, term infant via OVB following a TOLAC in Canada (excluding Québec), using administrative health data (2010-2021). Procedure codes were used to identify forceps and vacuum births. Modified Poisson regression with propensity score overlap weighting was used to estimate adjusted relative risks (ARR), accounting for clinical factors. SMM included diagnoses and procedures associated with high case fatality, extended length of hospital stay and long-term disability from the birth admission to 42 days postpartum.

RESULTS

Among 72,140 individuals with a TOLAC, 10,030 (13.9%) had an attempted operative vaginal birth (vacuum: 70.5%, forceps: 29.5%). SMM rates were higher with forceps vs vacuum (23.6 versus 14.1 per 1,000). In adjusted models, forceps use was associated with increased risk of SMM (ARR 1.58, 95% confidence interval [CI] 1.14-2.18). The two leading causes of SMM included severe hemorrhage (15.2‰ forceps vs 9.2‰ vacuum; ARR 1.55, 95%CI 1.03-2.34) and surgical complications (6.8‰ forceps vs 2.1‰ vacuum; ARR 3.55, 95%CI 1.75-7.20).

CONCLUSION

Among individuals with a TOLAC, forceps birth is associated with higher risk of severe hemorrhage or surgical complications versus vacuum. Patient counseling and clinical decision-making should incorporate maternal safety by instrument attempts in tandem with attaining vaginal birth.