The association between neonatal head circumference and second stage duration

Purpose: To determine if head circumference (HC) is an independent factor influencing second stage duration stratified by parity and epidural use.Materials and methods: A retrospective cohort analysis of all live, singleton, term (37-42 weeks) vaginal deliveries in one university affiliated medical center (2012-2014). Exclusion criteria included operative deliveries due to fetal distress, major fetal anomalies/chromosomal abnormalities or cases with missing anthropometric data. Maternal demographics, labor characteristics and neonatal anthropometrics including birth weight and HC were retrieved. Multivariate linear regression was utilized to evaluate the association between HC and second stage duration. Analysis was stratified into four groups by parity and epidural use.Results: Of the 16 240 singleton vaginal deliveries during study period, 12 428 deliveries met inclusion criteria. Stratification by parity and epidural analgesia yielded four groups: 3337 (26.9%), 735 (5.9%), 5099 (41.0%) and 3257 (26.2%) deliveries - nullipara with/without epidural and multipara with/without epidural, respectively. In all groups, a large neonatal HC was significantly and independently associated with longer second stage duration: nullipara with epidural (beta 10.06, 95% CI 7.75-12.37), nullipara without epidural (beta 7.58, 95% CI 4.73-10.43), multipara with epidural (beta 4.64, 95%CI 3.47-5.8) and multipara without epidural (beta 1.35, 95% CI 0.76-1.94), p < .001 for all. Birth weight was not associated with second stage duration in any of the groups (p > .05).Conclusion: Large neonatal HC is significantly associated with longer second stage duration.