Abstract :
[en] OBJECTIVE: Abnormal invasion of the placenta is more common after an elective Caesarean birth suggesting that pre-labour Caesarean section increases the likelihood of a scar above the internal cervical os - predisposing to a scar pregnancy in the future. The aim of this study was to assess the location and integrity of the uterine scar in postpartum women who delivered by Caesarean section at various stages of labour. METHODS: This was a prospective cohort study where women undergoing a first Caesarean section at term had a transvaginal ultrasound examination three months postpartum. The location of the Caesarean scar in relation to the internal cervical os was assessed as well as the presence of a scar niche. RESULTS: A total of 407 pregnant women were recruited into the study: 103 with cervical dilatation <2cm, 261 with cervical dilatation 3-7cm and 43 with cervical dilatation >8cm. There was a statistically significant correlation between cervical dilatation at the time of the section and the position of the uterine scar. The scar was positioned in the uterus above the internal cervical os in 97.1% (100/103) of women delivered at 0-2cm cervical dilatation, whereas the scar was located at or below the internal cervical os in 97.7% (42/43) of cases delivered at 8-10cm cervical dilatation (p<0.001). Uterine scar defects (niches) were observed in 38.1% (64/168) of women with the scar above compared to 17.9% (43/239) with the scar at or below the internal cervical os (p<0.001). CONCLUSION: Pre-labour and early labour Caesarean birth is associated with an increased prevalence of a scar in the uterine cavity as well as a scar niche. Caesarean birth in late labour resulted in positioning of the uterine scar in the endocervical canal and fewer scar niches. Positioning and integrity of the uterine scar after pre-labour and early labour Caesarean birth explains the predisposition to abnormal placental invasion in subsequent pregnancy. This article is protected by copyright. All rights reserved.
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