Obstet Gynecol Sci.  2024 Jan;67(1):1-16. 10.5468/ogs.23141.

Intrapartum transperineal ultrasound: angle of progression to evaluate and predict the mode of delivery and labor progression

• Jung JE
• Lee YJ

• KMID: 2550482
• DOI: http://doi.org/10.5468/ogs.23141

Abstract

Intrapartum ultrasonography serves as a valuable tool for the objective evaluation of labor progression and effectively identifies underlying factors, such as asynclitism, in cases of abnormal labor progression. Among the various ultrasound measurement techniques, the angle of progression (AOP) demonstrates favorable reproducibility and accuracy in assessing fetal head descent. In the context of abnormal labor, interventions differ across different stages of labor, emphasizing the importance of investigating the utility of AOP according to labor stages in this review article. Pre-labor assessment of AOP can be beneficial in terms of counseling for the timing of induction of labor, while a wider AOP value during the prolonged first stage of labor has demonstrated a positive correlation with successful vaginal delivery and shorter time to delivery. In the second stage of labor, the AOP has exhibited efficacy in predicting the mode of delivery and complicated operative deliveries. Furthermore, it has assisted in predicting the duration of labor, thereby highlighting its potential as a decision-making model for labor progression. However, further research is needed to investigate aspects, such as the determination of cutoff values, of AOP, considering the multifaceted characteristics of labor progression, which are influenced by complex interactions among maternal, fetal, and other contributing factors.

Keyword

Intrapartum; Ultrasound; Angle of progression; Labor; Delivery

Figure

• 

  Fig. 1 Characteristic features of the AOP on intrapartum transperineal ultrasound. (A) The angle measurement (white A) between the longest axis from the symphysis (red arrow) of the PB (white dot circle), which is ‘less echogenic’, to the bony part of the fetal head in the closest to the cervix, cervical canal (black arrow). (B) The angle (white A) using the longest axis from the ramus (red arrow) of the PB (white dot circle), which exhibits a higher echogenicity, to bony part of the fetal head, the cervical canal (black arrow). PB, pubic bone; A, angle; BL, bladder; FH, fetal head; CX, cervix; ms, mid-sagittal; AOP, angle of progression; ps, para-sagittal.

Reference

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