OC11.01: *Uterine contractility changes after successful embryo implantation

To assess if a certain uterine contractility profile after embryo transfer is associated with subsequent ongoing pregnancies in IVF/ICSI patients. This study entailed secondary analysis of a historic prospectively included cohort study of 16 IVF patients undergoing IVF treatment at the Ghent University Hospital in Belgium in 2016-2020. Each patient underwent a 4-minute transvaginal ultrasound 1 week after fresh ET of a good quality embryo. 2D-TVUS recordings were analysed using speckle tracking to extract a number of contraction features, namely contraction frequency, contraction amplitude, contraction velocity and contraction coordination. Features were compared between groups using the independent T-test or Mann-Whitney U test. Serum progesterone was associated with contraction features using Pearson correlation. 7/15 patients achieved ongoing pregnancy after ET. Age, BMI, number of previous IVF/ICSI cycles, gravidity, parity, serum progesterone at time of ET, endometrial thickness and subfertility duration were comparable for pregnant versus non-pregnant groups. In this small cohort of patients, patients with ongoing pregnancy showed relatively lower contraction frequency (0.925 vs. 1.168 contractions per minute, p = 0.037). Contraction amplitude, coordination and velocity were not significantly different between pregnant and non-pregnant groups. Increasing serum progesterone was significantly correlated to decreasing contraction frequency (Pearson correlation coefficient -0.714, p = 0.020). Patients with ongoing pregnancy 1 week after fresh ET show a distinctly different uterine contractility profile characterised by lower contraction frequency, likely in concordance with rising HCG levels. We also saw that contraction frequency seems to correlate directly to serum progesterone levels. This suggest contraction features can be an early predictor of successful ongoing pregnancy.