OC15.05: Evaluation of Subendometrial Wave Patterns in Women with a Niche in the Caesarean Section Scar Compared to Controls Without a Caesarean Scar

To evaluate the subendometrial contractions using ultrasound speckle tracking in women with a niche in the uterine Caesarean section (CS) scar compared to controls without a Caesarean scar, during the different phases in the menstrual cycle. Since contractions may play a role in the etiology of postmenstrual spotting and lower implantations rates in women with a niche. Retrospective case control study, matched for menstrual cycle phase. Women with a large niche (residual myometrium thickness (RMT) < 2mm) were compared to normal controls without previous CS. Recordings of 5 minutes of transvaginal ultrasound in the midsagittal plane were used for speckle-tracking analyses. Menstrual phases were registered; menses (ME); late follicular (LF); early luteal (EL); or late luteal (LL) phase. Speckle tracking by using 2D optical flow was performed. Primary outcome were amplitude features of the subendometrial contractions compared to controls, since a higher amplitude was previously correlated to lower ongoing pregnancy rates. Secondary outcomes were frequency and velocity of the contractions. 72 recordings were analysed (31 cases and 41 controls). The amplitude of the subendometrial contractions was significantly higher in women with a niche compared to the controls during all phases of the menstrual cycle (ME p = <0.001; LF p = < 0.001; EL p = 0.028; LL p = 0.003). Velocity was only lower in the women with a niche during LF phase (p = 0.012). Frequency was not different between the two groups. Contraction amplitude was higher in women with a niche compared to controls without a previous CS during all phases of the menstrual cycle. Changes in subendometrial contractions in women with a niche may play a role in the reported lower implantation rates and spotting and dysmenorrhea, compared to women without a niche. Future studies are needed to confirm this association.