Transabdominal ultrasound assessment of the fetal head and the accuracy of vacuum cup application.

OBJECTIVE: To investigate whether the accuracy of vacuum cup placement can be improved by intrapartum ultrasound assessment of the fetal head position during the second stage of labor prior to vacuum extraction for prolonged second stage. METHODS: 50 women undergoing vacuum extraction for prolonged second stage were randomly allocated to either digital examination (n=25) or digital examination together with transabdominal intrapartum ultrasound (n=25) prior to vacuum extraction by the attending obstetrician. The distance between the centre of the chignon and the flexion point was then measured by a midwife immediately after delivery. The flexion point was defined as 6 cm posterior to the anterior fontanelle or 3 cm anterior to the posterior fontanelle. RESULTS: There were no statistically significant differences in the demographic data, duration of labor, incidence of induction/augmentation, and intrapartum complications between the two groups. The mean distance between the centre of the chignon and the flexion point was 2.1+/-1.3 cm in the group with digital examination and ultrasound assessment and 2.8+/-1.0 cm in the group with digital examination alone. The difference in the mean distance between the two groups was statistically significant (p=0.039). CONCLUSION: Intrapartum transabdominal ultrasound assessment of the fetal head position during the second stage of labor improves the accuracy of vacuum cup placement during vacuum extraction for prolonged second stage.