Background
Data are scarce regarding the association between the presence of caput succedaneum and the mode of delivery.

Aims
To evaluate the presence and clinical significance of caput succedaneum thickness in prolonged second stage of labour.

Materials and Methods
We conducted a prospective study of women, beyond 37 weeks of gestation, during prolonged second stage of labour. Transperineal ultrasound was performed to assess the caput succedaneum thickness. The relationships between caput succedaneum thickness, feto‐maternal characteristics, delivery mode and immediate post‐natal outcomes were analysed.

Results
Fifty‐eight women, of whom 47 were nulliparas, in prolonged second stage of labour, were included in the study. The caput succedaneum thickness could be measured in all cases. Overall mean thickness was 21.9 (±4.9) mm (range 14–40 mm). No significant difference or correlation was found between caput succedaneum thickness, fetal head positions, modes of delivery, duration of second stage, head circumference or neonatal outcomes.

Conclusions
Caput succedaneum is measurable in all cases at prolonged second stage using transperineal sonography. Its presence and dimensions presented in our pilot study seem to have no implication on delivery mode and neonatal outcome.