Assessment of the progress of labor by the use of intrapartum ultrasound

Abstract

IntroductionCurrent obstetric practice strives to avoid difficult vaginal deliveries. The clinician's skill residing mainly in digital transvaginal examination is a subjective evaluation with several limitations. In recent years many reports have proposed a role for ultrasound in the evaluation of laboring patients. Aim of the workThe aim of this work was to assess the ability of intrapartum ultrasound to accurately and objectively monitor the progress of normal labor as well as to predict successful vaginal birth. Material and methodsThe current work included 200 full term singleton pregnant women in the active phase of the first stage of labor. All cases were in cephalic presentation and in occipitoanterior position. Per vaginum examination (PV) was first performed followed by transabdominal then translabial ultrasound visualizing the infrapubic plane. Ultrasound parameters were tested for the ability to detect the engagement of fetal head and for the occurrence of vaginal delivery. Several parameters were measured at rest and during the peak of uterine contraction. Results70.5% of patients considered PV worse than translabial ultrasound. For a cut-off of 22.3mm, the dynamic progression distance correctly identified cases that will deliver vaginally with a sensitivity of 74.4% and a specificity of nearly 82.9%. The dynamic angle of progression showed a sensitivity of 85.4% and a specificity of 88.7% at a cut-off of 112° to detect fetal head engagement. A statistically significant correlation was found between cervical diameter assessed using PV examination and using TLUS (r=0.75, p<0.001), as well as for the presence of caput and molding of the fetal skull. ConclusionIntrapartum ultrasound enabled the objective measurement of birth progress, providing a more scientific basis for assessing labor. This study has demonstrated the feasibility of defining a group of women at high risk of operative delivery.