Ultrasound studies of caesarean section scar in pregnancy
Creators: name: Naji, Osama
Publisher: name: Imperial College London
Year: 2013

description: Incomplete healing of CS scars has become a recognised sequel to this operation, and is associated with complications in later pregnancies. These can include caesarean scar pregnancy (CSP), a morbidly adherent placenta, scar dehiscence or rupture. To date there is uncertainty relating to the recognition of poor scar healing and the factors that lead to it. In recent years, there has been an increase in studies using ultrasound imaging to describe scars as deficient, or incompletely healed. However, these studies were carried out in the non-pregnant state, with a paucity of data to associate the described morphology of these scars to the functional integrity of the lower uterine segment (LUS) in subsequent pregnancy, or the actual performance in labour. We hypothesised that unenhanced transvaginal sonography (TVS) is a valid and reproducible method of assessing CS scars in pregnant women, and it can provide relevant clinical information on the effects these scars might have in pregnancy. To investigate the validity of TVS as the imaging modality of choice, we proposed a standardised approach for obtaining scar measurements. Furthermore we established a consensus agreement for nomenclature and methodology in imaging and reporting CS scars. We tested the reproducibility of the agreed methods throughout the course of pregnancy and our data showed that TVS could reliably delineate CS scar with good interobserver and intraobserver variability (IOV). We also investigated the influence of different scar dimensions on pregnant women from early pregnancy, during placental development, throughout the antenatal course and at delivery in terms of implantation sites, vaginal bleeding, and placental location, as well as the effects of scar changes on the final scar appearance at repeat CS, or during trials of vaginal birth after caesarean section (VBAC). Our data demonstrated that women who attended the early pregnancy assessment unit (EPAU) with a previous history of CS had more vaginal bleeding but similar spontaneous miscarriage rates in comparison to women without a history of CS. However, the implantation sites in the scarred uterus were significantly different from the non-scarred uterus. In the second trimester there were also significant differences in placental location. In the CS group there were more posterior and fewer fundal placentas than in the control group. We found that CS scars underwent significant changes to their shape and dimensions from the second trimester onwards. These scars were affected by the physical expansion of the gravid uterus and expanded accordingly in a cephalo- caudal pattern. Finally, we have demonstrated that certain scar measurements in the second trimester were associated with particular scar appearance at repeat caesarean delivery, and potentially predicted the likelihood of uterine scar rupture. We integrated this information and developed a prediction model on the likelihood of achieving successful VBAC from the earlier stages of pregnancy. In conclusion our data confirms that CS scar can be reliably assessed by ultrasound scan, and certain scar features are associated with complications that can be anticipated from as early as 6 weeks gestation. The results of our study provide important new information, which if validated externally may have significant bearing on our understanding of the impact of CS on the uterus, and the management of women planning to attempt a vaginal delivery after a previous CS.