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[Intrapartum Translabial Ultrasound: A Systematic Analysis of The Fetal Head Station in The First Stage of Labor].

INTRODUCTION
This prospective study aimed to define the angle of progression (AOP) in relation to the height position of the fetal head during the first stage of labour. It was investigated if it is possible to predict the mode of delivery or the duration of labour by AOP.


METHODS
Influencing factors on delivery were head circumference, birth-weight, administration of oxytocin, epidural anaesthesia (EA) and parity, and their impact on AOP was analysed. AOP was calculated using three different formulas. Inclusion criteria were vaginal delivery of singletons in cephalic, occipito-anterior presentation.


RESULTS
30/80 recruited women met the study criteria. 90% delivered spontaneously vaginally, 10% had instrument-assisted vaginal delivery. The average AOP in spontaneous vaginal deliveries was 100.9° at cervical dilation less than 5 cm, and 125.3° at cervical dilatation more than 5 cm. The average AOP in instrument-assisted births was 93° and 113.9° when the cervical os was less than 5 cm and more than 5 cm, respectively. Analysis identified a predictive trend towards the duration of labour only by use of the first AOP formula but not regarding the mode of delivery.


CONCLUSION
Sonographically assessed AOP during first stage of labour indicates trends regarding the duration of labour.