ATOSIBAN THE DAY OF EMBRYO TRANSFER MAY IMPROVE SUCCESS RATE IN PATIENTS OVER 1.5 UTERINE CONTRACTIONS PER MINUTE

Problem statement
Increased uterine peristalsis (UP) has been associated with poorer assisted reproductive treatments outcomes. This is mediated by higher level of oxytocin. Thus, the use of oxytocin antagonist as atosiban has been proposed to reverse this condition and increase the chance for the success. Thus, the use of atosiban when high uterine peristalsis is observed may improve success rate of these patients.
Methods
A retrospective cohort study has been carried out from 2017 to 2022 including 519 patients diagnosed with recurrent implantation failure undergoing frozen-thawed blastocyst embryo transfer. Hypercontractility group (HyperC) was defined as patients with 1.5 contractions per minute (cpm) or more. Uterine peristalsis has been assessed using 2D/4D ultrasound for 6 minutes the day of embryo transfer. Patients with HyperC underwent atosiban treatment as an IV bolus of 6.75 mg at approximately 10 min before embryo transfer.
Results
In our study 519 patients were enrolled with an average age of 40.5 years-old, 3.13 assisted reproductive treatments (ART), 3.38 embryo transfers and 4.1 embryos transferred. There were statistically significant differences between groups in the average of patients age, progesterone levels, endometrial compaction, type of endometrial preparation and the presence of endometriosis, so multivariate analysis was done adjusted by these factors. HyperC was found in 185 patients (35,6%), and all of them were treated with atosiban. Significantly higher biochemical pregnancy rate was observed in HyperC group (55,7% (103/185) vs 43,7% (146/334); OR 1,7; 95%IC 1,2 to 2,5; p=0,007). However, clinical pregnancy rate (41% (76/103) vs 34,4% (115/334)) , clinical miscarriage rate (17,5% (18/103) vs 15% (22/146)) and live birth rate ( 27,6% (51/185) vs 22,4% (75/334)) were comparable (p=0.42, 0,78, and 0,12, respectively).
Conclusion
In our study, patients treated with atosiban and uterine peristalsis frequency above 1.5 contractions per minute achieved higher biochemical pregnancy rate. However, similar live birth rates were achieved in patients with normal uterine peristalsis. This may be because atosiban reverses the effect of high UP frequency, which is associated with poorer outcomes. Our results encourage randomized trials focus on exploring atosiban treatment in patients suffering from increase uterine contractility.