INTRODUCTION
During the active second stage of labour, operative deliveries may be indicated for fetal distress or dystocia1. Obstetricians need to choose between an immediate caesarean section (C-section) and an attempt at operative vaginal delivery (OVD), which has an estimated failure risk from three to seven percent2–6.
The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine consider that OVDs performed by experienced operators are safe and acceptable alternatives to C-sections2. Mid-cavity OVDs are associated with more birth and obstetric trauma than low-cavity OVDs and C-sections7–10. Nevertheless, the ACOG and the Royal College of Obstetricians and Gynaecologists (RCOG) consider that mid-cavity OVD performed by experienced operators can be reasonable in selected cases. The French College of Gynaecologists and Obstetricians considers that the available scientific data are insufficient to contraindicate it2,10-13.
The majority of OVDs are conducted in classical delivery rooms14. According to the RCOG, mid-cavity OVDs have a higher failure risk. They should therefore be considered as a trial and conducted in a place where an immediate C-section could be undertaken10,13. A trial in an operating theatre could reduce the delay between failed OVD and C-section and thus reduce neonatal morbidity. However, in the case of a successful OVD, the delay associated with transfer to the theatre may worsen neonatal outcomes10,13. As specified in a Cochrane Review, the transfer decision is subjective, and no current evidence can influence the practice of mid­-cavity OVDs14.
Vacuum use has recently increased: the vacuum is now the most used instrument, particularly in Europe and in the United States15–18.
Risk factors for failed OVDs are well described and include a high station of the fetal head3,4,6,10, primiparity5, macrosomia3–6,10, prolonged labour5,19, high maternal weight10,19, labour induction5,19, prolonged pregnancy3, and the occiput-posterior position3,5,6,10. A score comprising these different factors could help obstetricians select women with a high failure risk, for whom an attempt at mid-cavity OVD should be conducted in the theatre, with additional precautions: anticipated extension of epidural analgesia and concomitant preparations of C-section equipment.
The principal objective was to identify risk factors strongly associated with failed mid-cavity vacuum-assisted delivery (VAD) and to construct a risk model that could be used to guide obstetricians in choosing between a standard delivery room or an operating theatre.
The secondary objective was to compare maternal and neonatal outcomes according to the place and the conditions of the VAD attempt.