(875) The Impact of Time of Day on Operative Vaginal Delivery Rate

Objective:
Despite a decrease in the rate of operative vaginal delivery (OVD), it remains a key obstetric skill and it is valuable to understand patterns of OVD utilization. We sought to identify if time of day at delivery impacts the likelihood of OVD.

Study Design:
A cohort of 132,203 deliveries from an academic health system from 2013-2024 was queried for delivery admissions with vaginal mode of delivery. Vaginal deliveries were classified as OVD, using forceps or vacuum, or spontaneous (SVD). Inclusion criteria were vaginal delivery and full data regarding mode of delivery and gestational age at delivery. Time of day at delivery was defined as day shift (0700-1859) and night shift (1900-0659). Bivariate tests of association were conducted to compare patient attributes by time of day at delivery using chi square tests. The primary outcome was the rate of OVD. Crude and adjusted odds ratios were calculated using logistic regression to assess the association between time of day and likelihood of OVD, adjusting for significant confounders.

Results:

In total, 85,556 vaginal deliveries were identified: 42,999 (50.3%) at night and 42,557 (49.7%) during the day. Bivariate tests showed patients delivered at night were more likely to have a hypertensive disorder of pregnancy and admit BMI >40 but were less likely to have OVD compared to those in the day (5.5% vs 6.5%; p< 0.001) (Table 1). Crude odds ratios showed that compared to SVD patients, OVD patients are less likely to have BMI >40, chronic HTN, preterm birth, public insurance, language barrier, or be non-married. OVD patients were more likely to have singleton gestations. After adjusting for confounders, delivery at night remained associated with a lower likelihood of OVD (aOR 0.83; CI 0.78-0.88). Interestingly, in the multivariate model, a language barrier was associated with increased likelihood of OVD.


Conclusion:
Among vaginal deliveries, the rate of OVD varied by delivery time. Differences in OVD rates was also seen based on insurance status, marital status, language, BMI, parity, and preterm birth.