Tweetable abstract
Simple models based on maternal height and ultrasound findings can predict the delivery mode and internal fetal head rotation.
INTRODUCTION
Operative deliveries are associated with increased maternal (obstetric hemorrhage, perineal injuries, wound infection) 1, 2and neonatal morbidity (neonatal seizures, and intracranial hemorrhage)2-6. It is important to monitor labor progress to prevent these maternal and neonatal complications 7. The conventional assessment currently relies on a serial digital examination, which has been demonstrated to be subjective, imprecise, and poorly reproducible 8, 9. Furthermore, digital vaginal examinations can also cause discomfort 10 and may introduce infection 9. Intrapartum ultrasonographic examinations have been introduced to complement assessments of labor progress 11.
Occiput posterior (OP) and occiput transverse (OT) positions account for 15 to 49% at the onset of labor 12-15, and in most cases, the fetal head will rotate spontaneously to the occiput anterior (OA) positions. Accumulating evidence implicates the persistent OP or OT position is associated with obstetric complications, including prolonged labor, operative delivery, postpartum hemorrhage and third or fourth-degree perineal lacerations16-18. The spontaneous internal rotation of the fetal occiput from the transverse or posterior position to the anterior position is associated with multiparity, a maternal age of fewer than 35 years, maternal stature, BMI, and newborn birth weight (<4000 g) 14, 19, 20. However, there is still no model, which can help predict successful fetal head rotation during the delivery.
In the last decade, various sonographic parameters have been proposed, including the angle of progression (AoP)21, head-perineum distance (HPD)22 and midline angle (MLA) 23. Several studies have reported that intrapartum ultrasonography is a reliable and noninvasive approach for determining fetal head position, station and descent 24-27. The AoP has been used to assess fetal head station and be predictive of spontaneous vaginal delivery or successful instrumental vaginal delivery28-31, and the MLA was associated with the fetal head station and rotation11.
In the majority of studies, a single assessment of sonographic parameters was performed in either the first or second labor phase30, 32-35. Moreover, few studies have developed predictive models associated with successful internal rotation and vaginal delivery. Therefore, the primary aim of the present study was to assess serial intrapartum ultrasound measurements at different time points during delivery for the prediction of the delivery mode in nulliparous women. A secondary aim was to develop a model to predict successful internal fetal occiput rotation.