Abstract
Background
The uterine incision-to-delivery interval represents the period of interrupted uteroplacental blood flow during cesarean delivery. Prior studies evaluating its association with neonatal outcomes have yielded inconsistent findings, often limited by small sample sizes, heterogeneous indications for delivery, and reliance on surrogate markers such as Apgar scores or cord gases rather than clinical morbidity.
Objective
To evaluate the association between the uterine incision-to-delivery interval and adverse neonatal outcomes in non-urgent singleton term cesarean deliveries.
Study Design
This retrospective cohort study included all singleton pregnancies delivered by non-urgent cesarean delivery at term (≥37 weeks) in a single tertiary medical center between 2017-2021. Deliveries performed for concern for fetal or maternal compromise (non-reassuring fetal tracing, failed operative delivery, cord prolapse, suspected abruption, uterine rupture, or placenta accreta), those with major fetal anomalies, fetal death, or missing key data were excluded. The uterine incision-to-delivery interval was categorized as routine (<120 seconds), prolonged (121-239 seconds), or excessive delay (≥240 seconds). The primary outcome was a composite of neonatal adverse outcomes, including respiratory support, therapeutic hypothermia, birth injury, or neonatal death. Secondary outcomes included umbilical artery cord gases and maternal outcomes among others. Multivariate Poisson regression with robust error variance estimated adjusted relative risks. Adjusted linear probability models were applied. Inverse probability weighting was applied for analyses involving umbilical cord gases.
Results
Among 38,057 deliveries, 5,850 (15.4%) met inclusion criteria. Of these, 3,923 (67.1%) had an incision-to-delivery interval <120 seconds, 1,691 (28.9%) had 121-239 seconds, and 236 (4.0%) had ≥240 seconds. Compared with <120 seconds, prolonged (121-239 seconds) and excessively delayed (≥ 240 seconds) intervals were associated with higher risk of composite neonatal adverse outcome (adjusted relative risk 2.18, 95% CI 1.28-3.70; and adjusted relative risk 3.39, 95% CI 1.42-8.09, respectively). Each additional minute of extraction increased the composite outcome risk by 0.6 percentage points (95% CI 0.4-0.8%; p<0.01). Weighted analyses for cord gases availability demonstrated that an interval ≥240 seconds was associated with umbilical artery pH <7.1 (adjusted relative risk 6.53, 95% CI 3.58-11.93) and base deficit ≥12 mmol/L (adjusted relative risk 11.02, 95% CI 3.71-32.74); each minute increased the probability of neonatal acidemia by 1.5 percentage points (95% CI 0.8-2.2; p<0.01). Sensitivity analyses showed consistent associations across prelabor and intrapartum cesarean deliveries, though with differing effect magnitudes. Maternal morbidity was similar across groups except for higher spontaneous hysterotomy extension rates in the ≥240-second group (adjusted relative risk 1.93, 95% CI 1.02-3.68).
Conclusion
Longer uterine incision-to-delivery intervals in non-urgent term cesarean deliveries were independently associated with increased risk of neonatal morbidity, as well as acidemia. The incremental rise in risk with each additional minute of extraction suggests a time-dependent relationship between incision-to-delivery duration and neonatal outcomes. Recognition of this additive effect and proactive anticipation of extraction difficulty may help improve perinatal care quality.