Pengbo Yuan, Shaohua Yin, Xiaoyue Guo, Jing Yang, L.T. Li, Yuan Wei, Yangyu Zhao
BACKGROUND: Higher maternal and neonatal mortality for women admitted to hospital on weekends than on weekdays was reported, but the associations in women delivered by cesarean remain unclear. OBJECTIVE: To examine the association between weekday-weekend cesarean delivery and perinatal outcomes in singleton pregnancies, and to assess modification by hospital factors (obstetric size, annual delivery volume, and intensity of obstetrician). METHODS: 9097 singleton pregnancies delivered by cesarean section in eight Chinese public hospitals from Jan2017 to May 2021 were included. Perinatal outcomes included postpartum hemorrhage, prolonged length of stay, preterm, and low birth weight, 5-minute Apgar score <7, and NICU admission. Multivariable logistic regression models were used to estimate adjusted odds ratios (aORs) with 95% confidence intervals (95% CIs). RESULTS: Among cesarean pregnancies (mean [SD] age, 36.7 [3.8] years), the rate of preterm was 13.8% (weekend 16.7% vs. weekday 13.4%; P=0.002), low birth weight was 6.8% (weekend 8.7% vs. weekday 6.5%; P=0.005) and NICU admission was 6.7% (weekend 8.4% vs. weekday 6.4%; P=0.009). After adjusting for sociodemographic, complications, and hospital characteristics, weekend delivery was associated with increased risks of preterm ( aOR 1.67, 95% CI 1.39-1.99), low birth weight (aOR 1.64, 95% CI 1.30-2.06), and NICU admission (aOR 1.52, 95% CI 1.20-1.91). These associations may partly explained by conditions such as preterm labor or fetal compromise on weekends - often the reason for urgent cesarean delivery, rather than reduced quality of weekend care. Associations were stronger in high-volume, larger obstetric units, although interactions were not statistically significant. CONCLUSIONS: While weekend cesarean delivery was associated with higher odds of adverse neonatal outcomes, these findings should not be interpreted simply as "weekend effect." In the absence of data on surgical indication and urgency, residual confounding by case mix remains likely, rather than reduced care quality. TRIAL REGISTRATION: NCT03220750, Registered July 18, 2017 - Retrospectively registered, https://classic. CLINICALTRIALS: gov/ct2/show/NCT03220750.