Unintended hysterotomy extension during caesarean delivery: risk factors and maternal morbidity.

We conducted an observational retrospective cohort study to evaluate the risk factors and the maternal morbidity associated with unintended extensions of the hysterotomy during caesarean delivery. We evaluated 2707 women who underwent low-transverse caesarean deliveries in 2011 at an academic, tertiary-care hospital. Hysterotomy extensions were identified through operative reports. Of the 2707 caesarean deliveries, 392 (14.5%) had an unintended hysterotomy extension. On the multivariable regression modelling, neonatal weight (OR 1.42; 95%CI 1.17-1.73), the arrest of labour [first-stage arrest (2.42; 1.73-3.38); second-stage arrest (5.54; 3.88-7.90)] and a non-reassuring foetal status (1.65; 1.20-2.25) were significantly associated with hysterotomy extensions. Hysterotomy extensions were significantly associated with an increased morbidity including an estimated blood loss >1200 millilitres (2.06; 1.41-3.02), a decline in postoperative haemoglobin ≥3.7 g/dL (2.07; 1.35-3.17), an evaluation for lower urinary tract injury (5.58; 3.17-9.81), and a longer operative time (8.11; 6.33-9.88). Based on these results, we conclude that unintended hysterotomy extensions significantly increase the maternal morbidity of caesarean deliveries. Impact statement What is already known on this subject? Maternal morbidity associated with caesarean delivery (CD) is significantly greater than that in vaginal delivery. Unintended extensions of the hysterotomy occur in approximately 4-8% of CDs and are more common after a prolonged second stage of labour. The morbidity associated with hysterotomy extensions has been incompletely evaluated. What do the results of this study add? We demonstrate a rate of hysterotomy extension in a general obstetric population of approximately 15%, which is higher than previously reported estimates, and represents a potential doubling of the rate of the unintended hysterotomy extensions in recent years. The most significant risk factor for a hysterotomy extension was a second-stage labour arrest with a fourfold increase in the frequency of extensions. A hysterotomy extension is a significant independent risk factor for an intraoperative haemorrhage, a drop in postoperative haemoglobin, an intraoperative evaluation for lower urinary tract injury, and longer CD operative times. What are the implications of these findings for clinical practice and/or further research? A second-stage arrest is a strong independent risk factor for a hysterotomy extension. Recent re-evaluations of the labour curve that extend the second stage of labour will likely increase the frequency of CDs performed after a prolonged second stage. In these scenarios, obstetricians should be prepared for an unintended hysterotomy extension and for the possibility of a longer procedure with the increased risks of blood loss and the need for evaluation of the lower urinary tract.