The Use of Two-Dimensional (2D) and Three-Dimensional (3D) Ultrasound in the First Stage of Labor

Abstract

Friedman’s labor partogram is the central pillar for clinical management of labor today. First published more than a half-century ago in 1955 [1], the partogram charts labor progression by the dilatation of the uterine cervix and descent of fetal presenting part over time in nulliparous and parous patients. Friedman divided labor into two stages: The first stage includes a preparatory division (latent phase) that begins with regular contractions and minimal cervical changes and a dilatation division (active phase) at which cervical dilatation advances at its greater rate, accompanied by some descent of the fetal presenting part. The second stage (the pelvic division) starts with cervical full dilatation and the final descend of fetal presenting part (Fig. 3.1) [2]. Physicians realized early on that digital examination alone was a poor tool for assessing changes in cervical dilatation and in the descent of the presenting part with low accuracy and poor reproducibility [3, 4]. In response several cervimetry devices for the objective measurements of cervical dilatation were proposed by Friedman himself and others [5, 6]. Yet, heretofore none of these attempts, all of which require vaginal instrumentation and expensive apparatuses, have been incorporated into routine clinical management of labor. Today, sonography is the most accepted and widely used imaging modality in obstetrics and gynecology with a proven capability to provide safe, fast, and accurate measurements of fetal and maternal anatomy. Mobile and portable ultrasound equipment adapted for bedside care are present in most, if not all, modern delivery rooms. It seems just natural that the technology could be applied to the clinical management of labor, meeting the need for an accurate and objective documentation of labor progression. Indeed, several researchers have used the imaging technique to investigate ways to provide accurate information in cervical changes and fetal stage and position in the first stage of labor. The aim of this chapter is to review these efforts to use two-dimensional (2D) and three-dimensional (3D) ultrasound in the first stage of labor.