Ultrasound diagnosis of fetal head engagement

Objective: To compare clinical data and transperineal ultrasound results for the diagnosis of fetal head engagement.

Methods: The present prospective longitudinal study enrolled 100 term women attending the Mongi Slim Hospital, La Marsa, Tunisia, between July and September 2012. The clinical assessment of fetal engagement was compared with ultrasound measurements. Ultrasound examination was performed in the delivery room. The probe was placed on the ano-vulvar area. The measure used was the distance between the perineum and external table of fetal skull.

Results: The ultrasound measures of the perineum to external table of fetal skull ranged from 13 to 75mm. The measures of the perineum to succedaneum bump ranged from 22 to 68mm. A threshold of 55mm was determined as the perineum to fetal head distance above which a diagnosis of engagement would be reversed. This proposed threshold had a positive predictive value of 98.6%, a sensitivity of 86.7%, and a specificity of 94.1%.

Conclusion: Transperineal ultrasound is a simple, rapid, and reproducible method for the diagnosis of fetal head engagement. It can be used in the delivery room in addition to clinical examination and when the latter is hampered by a succedaneum bump.