Abstract
Prolonged second stage of labor is a common abnormality of labor progression. Very little research exists regarding the relationship between prolonged second stage of labor and antepartum sonographic fetal head biometry parameters, especially fetal biparietal diameter (BPD). Fetal BPD assessment is essential for estimating fetal weight, and these measurements are readily available to Japanese obstetricians. We conducted a retrospective observational cohort study to evaluate the association between BPD fetal Z-score and prolonged second stage of labor in a Japanese cohort. Individual BPD data measured using a GE Voluson 730 expert ultrasound system (GE, Healthcare Japan, Tokyo, Japan) were converted to Z-scores for a particular gestational age. After excluding patients with multiple pregnancies and emergency or elective cesarean sections, a total of 2,711 (nulliparity, n = 1341) Japanese women who delivered at term were included. We analyzed the incidence of prolonged second stage of labor and the association between BPD Z-score measured <7 days before delivery and prolonged second stage of labor by parity. The overall incidence of prolonged second stage of labor was 18.3% (246/1,341) in nulliparous women and 4.6% (63/1,370) in multiparous women. In nulliparous women, multivariable analysis indicated that BPD Z-score was significantly associated with prolonged second stage of labor (adjusted odds ratio, 1.18; 95% confidence interval, 1.02-1.37). Kaplan-Meier survival analysis showed that at each time point during the second stage of labor, the percentage of women who had not yet delivered was higher among those who delivered neonates with large BPD Z-scores than among those who delivered neonates with smaller BPD Z-scores. On the contrary, in multiparous women, BPD Z-score was not statistically associated with prolonged second stage of labor. Our results suggest that considering BPD Z-score is helpful in the management of nulliparous women who are at risk of developing a prolonged second stage of labor.
Highlights
The second stage of labor is defined as the duration of time from full cervical dilatation to delivery of the new-born [1]
The formula is as follows: EFW (g) = 1.07 × BPD3 + 3.00 × 10−1AC2 × FL, where BPD stands for biparietal diameter, AC stands for abdominal circumference, and FL stands for femur length [16]
A multivariable logistic regression model was used to identify variables significantly associated with prolonged second stage of labor, because the purpose of this study was to investigate whether a clinically significant duration of second stage of labor is associated with a large BPD
Summary
The second stage of labor is defined as the duration of time from full cervical dilatation to delivery of the new-born [1]. Little research has been performed concerning the relationship between biparietal diameter (BPD) and prolonged second stage of labor [14]. Even with the same antepartum sonographic fetal head biometry parameter, it may be easier to use BPD to assess the risk for prolonged second stage of labor than to use HC in Japan. Improved understanding of the relationship between BPD before delivery and prolonged second stage of labor will provide clinically useful information for perinatal management in Japan. This is because, especially in Japan, there has been little research done concerning second stage of labor. The risk factors for prolonged second stage of labor and evidence about the guide for the second stage of labor are insufficient [17]
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