Establishing the accuracy and acceptability of abdominal ultrasound to define the foetal head position in the second stage of labour: a validation study.

OBJECTIVES: To compare the diagnosis of the foetal head position in the second stage of labour by ultrasound scan performed by a novice sonographer and by clinical assessment, to that of an expert sonographer (gold standard); and to evaluate the acceptability of ultrasound in the second stage of labour to women and clinicians. STUDY
DESIGN: This is a case series. We recruited sixty women delivering in a university hospital in Dublin, Ireland. An abdominal scan was performed by a novice and an expert ultrasonographer and a clinical assessment was performed by an obstetrician or midwife. Each assessor was blinded to the findings of the others. The main outcome measures were errors in the diagnosis of the foetal head position and acceptability of abdominal ultrasound in the second stage of labour.
RESULTS: The ultrasound findings of the novice and expert ultrasonographers were consistent in 52 (87%) cases for the foetal head position; 80% accuracy for the first ten scans performed by the novice (median time 150 s) and 90% for the last ten scans (median time 10s). The novice made no occipito-anterior/occipito-posterior (OA/OP) errors. The clinical diagnosis of the foetal head position was incorrect in 25 (42%) cases; 8 (13%) OA/OP errors. Women and clinicians did not consider the ultrasound assessment to be intrusive.
CONCLUSION: An abdominal scan by a novice ultrasonographer is an accurate and acceptable method of diagnosing the foetal head position in the second stage of labour and may have a role to play in assessment prior to instrumental delivery.