Intrapartum sonography to determine fetal head position

Abstract

Objective: To investigate the accuracy of intrapartum transvaginal digital examination in defining the position of the fetal head. Patients and methods: In 496 singleton pregnancies in labor at term, the fetal head position was determined by routine transvaginal digital examination by the attending midwife or obstetrician. Immediately before or after the clinical examination, the fetal head position was determined using transabdominal ultrasound by an appropriately trained sonographer who was not aware of the clinical findings. The digital examination was considered to be correct if the fetal head position was within 45° of the ultrasound finding. The accuracy of the digital examination was examined in relation to maternal characteristics and the progress of labor. Results: The position of the fetal head was determined by ultrasound examination in all 496 cases examined. Digital examination failed to define the fetal head position in 166 (33.5%) cases and, in 330 cases where the position was determined, the findings of the digital and sonographic examinations were in agreement in only 163 (49.4%) cases. The rate of correct identification of the fetal position by digital examination increased with cervical dilatation, from 20.5% at 3–4 cm to 44.2% at 8–10 cm, and was higher if the examination was carried out by an obstetrician than a midwife (50% versus 30%) and if there was absence rather than presence of caput (33% versus 25%). Conclusions: Routine digital examination during labor fails to identify the correct fetal position in the majority of cases.