Is there a correlation between time of delivery and newborn cord pH?

Purpose: Since more senior and attending physicians work in labor wards during morning shifts, we expect a better delivery outcome during that time period. Materials and methods: A retrospective study was conducted between 1/2005 and 12/2014. Records of 56 428 singleton deliveries from a tertiary hospital in which cord blood pH was routinely measured at birth were analyzed. Time of birth was divided into shifts: 7 AM-3PM (morning shift), 3 PM-11PM (afternoon shift), and 11 PM-7 AM (night shift). Additional stratification compared weekdays and weekend deliveries. Results: 19 601, 18 429, and 18 398 neonates were born during morning, afternoon, and night shifts, respectively. There was no significant difference in maternal age, neonatal weight, or mean 5-min Apgar score among the three shift periods. Furthermore, there was no correlation between shift time of delivery and newborn acidosis with respect to cord pH less than 7 (0.1% in each time periods, p = 0.67). Despite the above, instrumental deliveries and cesarean sections were more common in the morning shift compared to the afternoon and night shift, respectively (p = 0.001 each). Conclusions: Although shift time of delivery was found to be related to mode of delivery it was not related to either 5-min Apgar score or newborn acidosis as reflected by cord pH.