Ultrasound Assessment of Foetal Head–Perineum Distance Prior to Induction of Labour as a Predictor of Successful Vaginal Delivery
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In modern obstetrical practice, incidence of induction of labour is on rise for varied maternal and foetal indications. Ultrasound can help obstetricians in counselling patients before induction of labour and explain the probability of successful induction.
To study the role of foetal head–perineum distance in predicting successful vaginal delivery and to correlate with other parameters such as cervical length and Bishop score.
This study is a prospective case–control study in a tertiary care teaching hospital.
There were 250 term patients between 37 and 40+ weeks with singleton cephalic presentation with no contraindications for vaginal delivery.
Prior to induction of labour, transperineal ultrasound was performed to measure foetal head–perineum distance. Simultaneously, cervical length was performed using transvaginal ultrasound probe. Bishop score was determined at the same time by clinical examination.
Main Outcome Measures
Outcome of induction was considered successful when it resulted in vaginal delivery. It was considered to be a failure if patient did not get into active phase of labour or an operative intervention had to be performed because of non-progress of labour in active phase of labour. Cases were excluded if caesarean delivery had to be performed in the event of foetal distress.
It was observed that as the transperineal foetal head–perineum distance decreased, the rate of vaginal delivery increased. Similarly, when foetal head–perineum distance increased, the rate of caesarean delivery increased. At a cut-off ≤ 5.5 cm, foetal head–perineum distance had a maximum predictability (sensitivity 97%, specificity 88.1%).
Transperineal foetal head–distance measured by ultrasound can be used as an important tool to predict vaginal delivery before induction of labour.
KeywordsInduction of labour Transperineal ultrasound Foetal head–perineum distance
Authors would like to thank Manipal Academy of Higher Education for granting seed money to conduct this study.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
The study has been approved by institutional ethical committee of Manipal Academy of Higher Education.
Human and Animal Rights
This study does not involve any research work involving animals and was performed on term pregnant women undergoing induction of labour.
Informed consent has been obtained from all participating subjects prior to study.
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