METHODS
We conducted an observational analytical predictive prospective monocentric study of attempts at mid-cavity VAD performed between January 2010 and December 2018 in the Maternity Unit of the University Hospital of Besançon, France.
All attempts at mid-cavity VAD with epidural analgesia, after 37 weeks of gestation, in singleton pregnancy with a vertex presentation were included. The mid-cavity was defined as a fetal head that was no more than one-fifth palpable per the abdomen and a leading point of the skull above station plus two centimetres but not above the ischial spines10,13. In our study, this corresponded to a head-perineum distance measured by trans-perineal ultrasound that was greater than or equal to 40 mm at the beginning of the VAD, without compression of the soft tissue against the pubic bone, as described by Maticot-Baptista et al. and ISUOG20,21. We also included the few high-cavity VADs defined by head-perineum distances greater than 60 mm.
The safety conditions for performing a mid-cavity VAD were strict and corresponded to our usual practices: performance of the VAD by a senior obstetrician, with preliminary ultrasound verification of the fetal head position and station, with placement of appropriate analgesia, alerting of the anaesthetist and paediatrician, informing the woman of the possibility of failure, and obtaining her verbal consent. The obstetrician decided on the conditions of the VAD attempt: type of room and eventual concomitant preparation of C-section equipment. The eventual anticipated extension of epidural anaesthesia was either requested by the obstetrician or decided by the anaesthetist to reduce the incision delay in case of C-section. It corresponded to a first epidural top-up administered during the preparation or the realization of the VAD before the potential decision of C-section: clonidine 50 to 75 µg and/or lidocaine 2 % 5 cc and/or sufentanil 5 to 10 µg, depending on the anaesthetist’s preference. In case of failed VAD, a second top-up was administered just after the C-section decision. In case of failed VAD in a classical delivery room, women were transferred to the surgical room for the C-section.
Both successful and failed attempts leading to an emergency C-section were included. Sequential uses of instruments (failed VAD followed by successful spatula- or forceps-assisted delivery) were considered successful attempts.
The study was approved by a local ethical committee (Comité de Protection des Personnes Est II) and by the French data protection agency (CNIL: Commission nationale de l’informatique et des libertés) under report number 2051119v0. The study was registred on ClinicalTrials.gov (identifier: NCT03853499).
No specific funding was received for this study.