Measurement of Angle of Descent (AOD) by Transperineal Ultrasound in Labour to Predict Successful Vaginal Delivery.

INTRODUCTION

Non-progress of labour forms the largest indication caesarean section. The diagnosis of failure of descent using serial digital examination is objective, poor reproducibility, carries the risk of infection and is painful to the labouring patient. There is a need if not an alternative, adjunctive to digital vaginal examination. Measuring angle of descent (AOD) to predict vaginal birth in late labour by transperineal ultrasound provides an alternative without any of the above-mentioned drawbacks.

MATERIALS AND METHODS

A prospective observational study in 64 patients in the late first stage and second stage of labour with cephalic presentation was carried out, from September 2017 to December 2018, in PGIMER and DR. RML Hospital. Angle of descent was measured by transperineal ultrasound. Angle of descent is the angle between the longitudinal axis of pubic bone and a line joining the lowest edge of the pubis to the lowest convexity of the foetal skull. Time of assessment of AOD was noted, and if patient did not deliver within 2 h, another AOD was recorded. Eighty-five readings were obtained, and AOD predicting successful vaginal delivery was calculated.

RESULTS AND DISCUSSION

AOD of 116° and more resulted in vaginal delivery, spontaneous or instrumental. As the angle of descent increased, there was a decrease in time interval to vaginal delivery with correlation coefficient of - 0.939.

CONCLUSION

The use of intrapartum transperineal ultrasound and measurement of angle of descent can prove to be a valuable adjunct in management of labour, especially in cases of prolonged first and second stages of labour in predicting successful vaginal delivery. AOD of 116° or more can predict successful vaginal delivery within 2 h. AOD can be used in centres having facilities of intrapartum ultrasound. The authors recommend the use of ultrasound in labour room as it is non-invasive and can provide a lot of information. This method is currently useful for tertiary centres or medical colleges.