Intrapartum Ultrasound to Differentiate Flexion and Deflexion in Occipitoposterior Rotation.

OBJECTIVE: To evaluate the ability of intrapartum ultrasound to differentiate occipitoposterior (OP) rotation with normal flexion of the head from deflexion, to compare the accuracy of ultrasound with the digital examination, and to assess the outcome of labor according to the type of presentation.

PATIENTS AND METHODS: A retrospective study of patients with abnormal labor because of either prolongation and/or abnormal cardiotocography and OP rotation who underwent intrapartum sonography.

RESULTS: Normal flexion was inferred in 36/42 cases by a longitudinal sonographic view of the fetal face demonstrating the chin approaching the chest. In the remaining 6, deflexion was diagnosed by visualizing the chin separate and distant from the chest. In 3 of these cases, the orbits were at the same level of the pubis suggesting brow presentation. In the remaining 3 cases, the orbits were above the pubis, and sinciput presentation was inferred. Head deflexion was diagnosed more accurately with ultrasound than clinically and always required a cesarean section versus 36% of cases with OP flexed presentation (p = 0.0052).

CONCLUSIONS: Fetuses with abnormal labor and OP rotation had deflexed presentations in 14% of cases and were never delivered vaginally. Sonography was far more accurate than the digital examination.