P-402 Comparison of uterine contractions in artificial hormone treatment versus aromatase inhibitor stimulated frozen embryo transfer cycles
Authors: Simsek E , Aytac P , Durdag G , Yaginc D , Yetkinel S 
Published: July 2024

Abstract

Study question
does uterine contractions differ between aromatase inhibitor stimulated (AIS) or artificial hormone treatment (AHT) Frozen Embryo transfer (FET) cycles

Summary answer
uterine contraction activity did not show any difference between artificial hormone treatment and aromatase inhibitor stimulated FET cycles

What is known already
FET cycles are prepared by different protocols. aromatase inhibitor stimulated (AIS) or artificial hormone treatment (AHT) protocols are two common protocols among others. These protocols have different cycle dynamics and might differ in pregnancy rates and different effects on perinatal outcomes. Although embryo related factors are most important for implantation endometrial receptivity and therefore uterine contractions might have a role in implantation. English literature provides scarce data on uterine contractions and pregnancy outcomes. Presence of prominent contractions were related to poor pregnancy outcomes in some studies whereas other few studies failed to show any effect in this sense

Study design, size, duration
this study is an observational cohort study of successive frozen embryo transfer (FET) cycles of eligible patients between 1st of july 2023 to 31th of October 2023 in a tertiary university hospital in vitro fertilization clinic with ultrasonographic video recordings at transfer day. During study period of four months, 147 out of 265 consecutive FET cycles were included in this study and study is approved by local ethical committee of the affiliated university (KA23/388).

Participants/materials, setting, methods
Total study group was composed of 99 artificial hormone treatment cycles and 48 aromatase inhibitor stimulated FET cycles after exclusion of patients with uterine congenital malformations, uterine fibroids,adenomyosis patients and patient with previous uterine surgery. Implantation rates, pregnancy rates and clinical pregnancy rates were recorded. Transvaginal ultrasonographic sagittal uterine video image recordings were obtained at transfer day one hour before embryo transfer. Recordings were reviewed by two researchers and uterine contractions were documented by agreement.

Main results and the role of chance
This is the first study comparing different FET cycles and uterine contraction activities. Patient characteristics were similar between two groups. Artificial hormone treatment and aromatase inhibitor stimulated cycle groups showed similar endometrial thicknesses (11.47±1.92 and 11.24±1.02, respectively p = 0.42) and top quality embryo transfer rates (22.6 % and 26.8% p = 0.82). Although AIH group showed a statistically insignificant advantage, clinical and ongoing pregnancy rates were similar between protocols (supplementary data). Uterine peristaltic activity was not statistically different between aromataze inhibitor stimulated and artificial hormone treatment FET cycle (1.54±1.75 versus 1.63±2.15 p = 0.81 recpectively). Furthermore uterine persistalsizm were similar in pregnant and non-pregnant patients /1.52±2.07 vs 1.72±1.93 p = 0.57). However as far as Aromatase inhibitor stimulated FET cycles were considered; pregnant patients had less uterine peristaltic activity when compared ton non-pregnant patient (45.7% and 15.4%, respectively p = 0.054 ) although this difference was at the border of statistical significance.

Limitations, reasons for caution
This is an observational study of relatively short duration with limited number of patients. Our study in AIS cycles have a tendency to fewer contractions in cycles ended up in pregnancy. Larger series of FET cycles might prove differences in uterine contraction frequencies and pregnancy outcomes in AIS FET cycles.

Wider implications of the findings
Our study supported new information on uterine contractility in different FET cycles protocols. Further large scale studies might provide new insights to uterine factor and its role in implantation as far as uterine contraactions are concerned.

Trial registration number
(KA23/388) local ethic committee approval