351: The association between head circumference and second stage duration

Abstract

Large neonatal head circumference (HC) is suggested to be associated with cesarean and instrumental delivery. We aimed to determine if HC is an independent factor influencing the second stage duration stratified by parity and epidural use. 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 of HC to second stage duration. Analysis was stratified to 4 groups by parity and epidural use. Of the 16,240 singleton vaginal deliveries during study period, 12,428 deliveries met inclusion criteria. Stratification by parity and epidural use yielded 4 groups: 3,337(26.9%), 735 (5.9%), 5,099(41.0%) and 3257 (26.2%) deliveries for nullipara with/without epidural and multipara with/without epidural, respectively. Rates of labor induction, oxytocin use, prolonged second stage and vacuum extraction due to prolonged second stage were significantly higher in nullipara with epidural compared to the other groups, p<0.001 for all. (Table 1). After adjusting for maternal age, induction of labor, neonatal gender, birth-weight and HC - multivariate linear regression demonstrated significant association between neonatal HC and second stage duration for all groups (p<0.05). For nulliparas with epidural- HC, maternal age and induction of labor entered the final equation; for nullipara without epidural- HC and maternal age entered the final equation and for both multiparas groups, HC was the single significant variable associated with second stage duration. In all groups and from all variables that entered the regression- HC had the largest B value suggesting its high impact on second stage duration. (Table 2) Large neonatal head circumference is significantly associated with longer second stage duration. Our study suggests it is the third most important determinant influencing the second stage duration after parity and epidural use.View Large Image Figure ViewerDownload Hi-res image Download (PPT)