Intrapartum Ultrasound Parameters (Ultrasonographic Semeiotics)

During the last decade, the value of ultrasounds has been confirmed for the diagnosis of feto-maternal disease and extended to the intrapartum examination. Ultrasound in labor can improve the assessment of fetal head position during labor [1]. The ultrasound examination can be performed during both the physiologic and dystocic delivery; it is a reliable technique, able to predict the possible complications of labor, thus allowing to choice the best management promptly. Several studies confirmed the reliability and utility of ultra- sounds in the delivery ward, where it is able to implement the routine clinical assessment. The manual obstetric evaluation is not replaced in the assessment of feto-maternal relation- ship and diameters, such as the external abdominal palpation according with the four Leopold’s maneuvers, the “in vivo” assessment of the obstetric pelvis to evaluate the competence of the birth canal and the pelvic diameters (Fig. 11.1). Ultrasounds offer the option of a complementary exami- nation, able to improve the monitoring of first and second stage of labor. Rayburn et al. demonstrated the ultrasounds’ better accuracy in the assessment of fetal head position if compared to the digital obstetric examination [2], affected by a high rate error in the identification of the fetal head station, especially in case of head remodelling and presence of caput succedaneum. Kilpatrick observed that the accuracy of vagi- nal examination can be affected by the cervical shortening that compromises the palpation of the fetal presented part and ischial spines; contrarily, this is not happening with intrapartum ultrasound [3]. The recent literature refers to the classical partogram as poorly reliable, affected by the subjectivity of obstetric assessment, and supports the necessity of a more objective evaluation. An objective and documented examination is essential nowadays, especially at the light of a growing med- icolegal issue: ultrasounds allow to assess objectively the A. Vimercati (*) · F. M. Crupano · M. Calabretti · E. Cicinelli 2nd Unit of Obstetrics and Gynaecology, Department of Biomedical and Human Oncological Science, University of Bari, Bari, Italy ongoing labor and to store pictures of fetal position and pos- sible dangerous situations, so supporting the clinician choice and obstetric management [4]. All the above observations give reason of the increasing use of ultrasounds in the delivery ward; nevertheless it is important to keep in mind that also the ultrasound assess- ment is subjective, and despite its potentiality, it cannot replace the clinical assessment that should always be per- formed when approaching the patient, before every instru- mental examination. The knowledge of specific ultrasound reference points allows to detail precisely the relationship between the fetal head and maternal pelvis and to follow the progression of labor, quickly detecting possible critical issues [5]. Several experts have been looking for similar parameters, so describ- ing various pelvic and ultrasound indexes; all of them are assessed by the translabial scan (Fig. 11.2), and the most sig- nificant described in literature are the following: • Angle of progression (AoP) • Head progression distance (PD) • Fetal head direction • Head-perineum distance • Head-symphysis distance (HSD) • Midline angle (MLA) • Pubic arch angle (PAA)