Effect of increased oxytocin doses on the mode of delivery in obese primiparous women with spontaneous or induced labour. A double-blind, randomised, controlled trial (PROXYMA).

backgroundThe prevalence of obesity in pregnancy is increasing worldwide, and it is associated with significant morbidity during labour and delivery. A benefit of increased doses of infused oxytocin during labour in obese women has been suggested by retrospective or underpowered studies. Thus, we aimed in a randomized double-blind controlled study at evaluating whether an increased oxytocin dose (compared to a standard dose) can reduce the rate of caesarean section without increasing maternal or neonatal morbidity.

methodsPROXYMA is a French national multicentre, randomized, double-blind, controlled trial conducted in 14 maternity units. Adult primiparous obese women (body mass index ≥ 30 kg/m2) with singleton pregnancy, spontaneous or induced onset of labour, cephalic presentation and term, ≥ 37 weeks of gestation, will be included after informed consent. Exclusion criteria are medical contra-indication for oxytocin or hypersensitivity, previous coagulation disorders, foetal growth restriction (inferior to 5th percentile), foetal major malformation or heart rate abnormalities before use of oxytocin (at the time of inclusion), scarred uterus of gynaecological origin, planned caesarean section before labour, or severe renal failure. Patients will be randomized in a 1:1 ratio and receive either high-dose (experimental group) or standard-dose (control group) oxytocin from prescription until delivery, with increments at least every 20 min, and oxytocin will be stopped instantly at birth. The inclusion of the patient and randomization of the oxytocin dose to be administered will take place at the time of the oxytocin prescription. An “out-of-protocol” healthcare professional (midwife / nurse) will be in charge of the preparation of the treatment, in order to ensure the double-blind design. The primary outcome will be the caesarean section rate in each group. Secondary outcomes include the comparison of maternal, foetal and neonatal-related complications during labour and birth. We aim at including 882 women based on a reduction in caesarean section rate of 7% in the experimental group, with a power of 80% and an alpha risk of 5%. DISCUSSION: Comparing two different oxytocin doses will provide clinicians with better knowledge of labour management in obese primiparous women to reduce the number of caesarean sections and associated morbidity.

trial registrationClinical Trials NCT04760496, registered on 18th february 2021. PROJECT CODE NUMBER: APHP200003 / EUDRACT No. : 2020-002640-23. Protocol Version N° 6.0 of 03/09/2024.