Joint impact of daily volume and weekend delivery (model 2*) on perinatal outcomes
| Outcome | Low/average-volume weekday | High-volume weekday | Low/average-volume weekend | High-volume weekend |
|---|---|---|---|---|
| Model 2 (interaction model) | ||||
| Maternal | ||||
| Obstetric infection | Ref. | 0.98 (0.94 to 1.02) | 1.06 (1.02 to 1.10) | 1.24 (1.12 to 1.37) |
| Haemorrhage | Ref. | 0.95 (0.91 to 0.98) | 1.02 (0.98 to 1.06) | 1.11 (1.01 to 1.22) |
| Severe perineal laceration | Ref. | 0.98 (0.95 to 1.02) | 1.09 (1.04 to 1.14) | 1.02 (0.91 to 1.13) |
| Prolonged LOS† | Ref. | 1.03 (0.99 to 1.07) | 1.19 (1.15 to 1.23) | 1.38 (1.28 to 1.49) |
| Composite maternal | Ref. | 0.99 (0.96 to 1.01) | 1.10 (1.08 to 1.13) | 1.20 (1.14 to 1.27) |
| Neonatal | ||||
| Birth trauma | Ref. | 0.99 (0.95 to 1.04) | 0.99 (0.95 to 1.03) | 0.99 (0.90 to 1.08) |
| Neonatal seizures | Ref. | 1.33 (1.01 to 1.74) | 1.11 (0.83 to 1.49) | 1.03 (0.62 to 1.71) |
| Apgar score <7 | Ref. | 1.02 (0.94 to 1.10) | 1.11 (1.03 to 1.21) | 1.29 (1.10 to 1.52) |
| NICU admission | Ref. | 0.98 (0.93 to 1.03) | 1.06 (1.02 to 1.10) | 1.11 (1.01 to 1.21) |
| Neonatal death | Ref. | 0.91 (0.78 to 1.07) | 1.02 (0.88 to 1.19) | 0.72 (0.46 to 1.12) |
| Composite infant | Ref. | 0.98 (0.95 to 1.02) | 1.03 (1.00 to 1.06) | 1.06 (0.99 to 1.14) |
Bold typeface indicates p<0.05.
*Results are OR (95% CI); model controlled for hospital volume category, maternal race/ethnicity, advanced maternal age, education, parity, insurance status, prenatal care and teaching hospital. Models estimated robust SEs accounting for hospital-level clustering.
†Prolonged LOS defined as LOS >3 days for vaginal deliveries and >5 days for caesarean deliveries.
LOS, length of stay; NICU, neonatal intensive care unit.