Quantification of fetal head direction using transperineal ultrasound: an easier approach

Abstract

Quantification of fetal head direction using transperineal ultrasound: an easier approachUltrasound offers several advantages for planning and monitoring labor, being a safe, non-invasive and easyto-learn technique, which offers accurate and objective information, even in difficult clinical situations. Several linear measurements (progression distance and head-toperineum distance) and angles (head direction (HD), progression angle and middle-line angle), have been shown to be useful in the estimation of fetal head progression 1 -10 . The rationale for assessing HD during the second stage of labor is the curvilinear path of fetal head descent, directed initially downward then horizontally and finally upward, that can be easily tracked in the sagittal transperineal view. Alone or in combination with other ultrasound parameters, HD has proved useful in the prediction of vaginal and successful operative delivery 4,10 . The abovementioned linear and angle assessments can be obtained in a semiautomatic manner, using threedimensional ultrasound 11 , but this is not widely available for use on the labor ward, requires additional skills to perform and has not been shown to provide further benefit over two-dimensional ultrasound 12 . Most of these linear distances and angles can be determined quickly and simply by measuring a single angle (progression angle, middle-line angle), a single distance (head-to-perineum distance) or a combination of a 90• angle and a line (progression distance). However, a recent systematic review 13 does not wholly support the use of ultrasound in labor and there is an argument that some measures are too complicated. For example, for quantification of HD, first the maternal reference parameter, the infrapubic line (IL), is drawn perpendicular to the symphysis pubis long axis (SPla), starting from the inferior symphyseal margin. Then the fetal parameter, the widest head diameter, is traced. Fetal head descent with respect to the pubic symphysis and IL is evaluated by drawing a line perpendicular to the widest diameter of the fetal head, i.e. HD. Finally, this parameter is quantified by measuring the direction angle (DA) between the IL and the HD 11,14 . In some studies 4,10 , HD is classified in this final step in relation to the SPla: 'head up' (when it points ventrally at an angle of > 30• ), 'head down' (when this angle is < 0 • ) and 'horizontal' (when this angle is 0-30• ). We propose an easier assessment of DA, by reducing the number of steps in the protocol. In Figure 1 we show how the classical measurement is equivalent to the angle between the fetal biparietal diameter and SPla. Thus, the steps described above can be substituted by the measurement of one angle between two lines similar, for example, to measurement of the fetal cardiac axis (Figure 2). Increasing values of this angle signify Figure 1 Classical fetal head direction angle (angle DA1), between infrapubic line (IL) and head direction (HD), is equal to angle between biparietal diameter (BPD) and symphysis pubis long axis (SP...

Intrapartum ultrasound and mother acceptance: A study with informed consent and questionnaire

“…In last years, an ultrasound pelvimetry has been developed, which considers angles and distances, to evaluate the descent, internal rotation of the fetal head. The parameters most used in clinical practice are: the Angle of Progression [36] , the angle of Internal Rotation [37] , the symphysis pubis distance [38] and the direction of the fetal head in the pelvis [39] , [40] . Patients who labor under neuraxial analgesia(NLA) with visual feedback have more acceptance of a prolonged labour [41] .…”

Prediction of labor outcome pilot study: evaluation of primiparous women at term

“…Rizzo et al 28 proposed US assessment of the fetal HC and maternal subpubic angle obtained from a reconstructed coronal plane on 3D US performed translabially at 36 to 38 weeks of gestation. 29 In this pilot study, we attempted to involve as many significant variables of the labor mechanism as possible, but we also had to take into account the general limitations of the maternity centers; therefore, we did not consider 3D acquisitions and interpretations.…”

Quantification of fetal head direction and descent

“…We read with interest the letter by Dr Iliescu et al 1 about a simplification of the assessment of head direction as depicted by intrapartum translabial ultrasound (ITU). We would like to caution against introducing supposedly easier approaches (angles) for intrapartum head descent.…”