(942) Risk factors and maternal morbidity associated with hysterotomy extension at time of cesarean delivery

To evaluate the association between hysterotomy extension at time of cesarean delivery in low-risk nulliparas and maternal morbidity. Secondarily, to identify risk factors for hysterotomy extension in this population.

Study Design:
This was a secondary analysis of the MFMU ARRIVE trial, a multi-center randomized trial of induction compared with expectant management among low-risk nulliparas at term. Those undergoing cesarean delivery with a low transverse hysterotomy were included in this analysis. The exposure was hysterotomy extension (both intentional and unintentional). The primary outcome was a maternal morbidity composite of infection, hemorrhage and intensive care unit (ICU) admission. Secondary outcomes included components of the primary and a neonatal morbidity composite. Multivariable modeling estimated the association between hysterotomy extension and outcomes with odds ratios and 95% confidence intervals reported. Candidate risk factors for hysterotomy extension were also evaluated.

Results:
Of 1,234 patients included, hysterotomy extension occurred in 76 (6.2%). Baseline characteristics were similar between those with and without hysterotomy extension (Table 1). Hysterotomy extension compared with no extension was associated with maternal morbidity (34.2% vs. 19.6%, OR 2.13, 95% CI 1.30-3.50; aOR 1.8, 1.08-3.00), and all individual components of the composite. Hysterotomy extension was not associated with neonatal morbidity (23.7% vs. 21.2%, OR 1.15, 95% CI 0.67-1.99; aOR 1.05, 0.60-1.84). No statistically significant risk factors for hysterotomy extension were identified.

Conclusion:

In a population of low-risk nulliparas undergoing cesarean delivery, hysterotomy extension was associated with increased maternal morbidity but not neonatal morbidity. There were no statistically significant risk factors for hysterotomy extension identified. It remains unknown whether hysterotomy extension is a consequence of other clinical factors which predispose to these complications, or if it is the hysterotomy extension itself that results in morbidity.