Diagnosis of fetal occiput position using transperineal ultrasound

To compare Transperineal (TP) and Transabdominal (TA) ultrasound in the assessment of fetal head position during the second stage of labor.

A prospective comparative Study including low risk parturients. The assessment of fetal head position was performed for each patient at full dilation. The ultrasound examination was performed by one examiner using TP technique first then TA. A routine digital vaginal examination was performed by a different examiner blinded to ultrasound findings. Considering TA as reference, the three methods were compared.

Fifty two patients were enrolled in the study group. Agreement between the clinical examination and TA ultrasound was average with Kappa index = 0.579. Agreement between TA and TP Ultrasound was good with Kappa index = 0.766. TP technique was accurate in the diagnosis of fetal head position (sensitivity =91.3%, specificity=98.38%, PPV=87.5%, NPV=98.91%). TA ultrasound was the most reliable method in case of high presentations. For lower fetal presentations, the TP approach was more relevant.

Assuming that an accurate diagnosis of fetal head position is required before any instrumental delivery where, by definition, fetal presentation is engaged, the TP ultrasound is advised. In a single time this technique provides the necessary information about the station, and the position of the fetal head.