Role of intrapartum ultrasound in modern obstetrics – current perspectives and literature review

For many years, the progress of labour has been traditionally evaluated almost exclusively by transvaginal digital assessment which, by its very nature, is an imprecise and, above all, subjective examination. Appropriate assessment of foetal head station and position in the birth canal is of critical importance for predicting further progress and safe completion of labour by instrumental or surgical intervention. In view of the deficiency of diagnostic methods available in the delivery room, attempts are undertaken to introduce intrapartum ultrasound performed using a transabdominal suprapubic or transperineal approach as a useful diagnostic tool. The examination is performed at the patient’s bedside, using a portable ultrasound unit equipped with a convex probe. The method comprises a range of parameters, of which the most common are the angle of progression (AoP), foetal head direction, head-perineum distance or midline angle (MLA). Intrapartum sonography yields an array of data to evaluate with a high degree of precision the foetal head position and station in the birth canal. Intrapartum ultrasound may prove a very useful method complementing traditional obstetric examination in a number of clinical situations such as prolonged delivery and lack of certainty as to the way to end the labour. Increasingly, attention is being drawn to the role of the examination in predicting the efficacy of induction of labour, serving as visual biofeedback to increase the effectiveness of maternal pushing or accurately identify the beginning of labour. It has been highlighted that intrapartum ultrasound is easy to use, painless, and reproducible. Also, the method does not require specialist training. Despite promising research results and the development of recommendations on the application of the method, there is still insufficient evidence to elaborate definite algorithms for the interpretation of results, based on which clinical decisions could be made.