Increased amplitude of subendometrial contractions identified by ultrasound speckle tracking in women with a caesarean scar defect

Research question: What is the effect of a caesarean scar defect on subendometrial contractions? Design: Prospective cohort study in a Dutch medical centre including women with a niche in the uterine caesarean section scar. Data were compared with controls without a caesarean section scar. All women underwent a 5-min recording by transvaginal ultrasound at four phases in the menstrual cycle: during menses; late follicular; early luteal; or late luteal phase. Uterine motion analysis was evaluated by dedicated speckle tracking using two-dimensional optical flow. Main outcome: amplitude of the subendometrial contractions. Results: Thirty-one women with a niche in the uterine scar and 11 controls, matched for menstrual cycle phase, were included. The amplitude of the subendometrial contractions was significantly higher in women with a niche compared with controls during all phases of the menstrual cycle (menses P < 0.001; late follicular P < 0.001; early luteal P = 0.028; late luteal P = 0.003). Velocity was lower in women with a niche during late follicular phase only (P = 0.012). A positive correlation between niche sizes (depth, length) and amplitude of subendometrial contractions was found. Conclusion: Subendometrial contractions were affected in women with a niche in the caesarean section scar compared with women who had not undergone a previous caesarean section. Contraction amplitude was higher and independent of the menstrual phase. These findings may cause postmenstrual spotting, dysmenorrhoea and lower implantation rates in women with a niche. Future studies should investigate this association and the underlying pathways.