A Sustainable Translational Sheep Model for Planned Cesarean Delivery of Contraction-Free Ewes

We evaluated whether the sheep constitutes a useful translational model to evaluate anatomical and surgical aspects of cesarean delivery (CD) from a human medical perspective with the aim of both maternal and neonatal well-being. Our hypothesis was that CD in contraction-free ewes is not associated with major complications. Primary endpoint was the transferability of anatomical conditions and surgical techniques of CD from the ewe to the human. Secondary endpoints were maternal and fetal survival, occurrence of retained fetal membranes, metritis, mastitis, or wound infections. Forty-eight Merino ewes were delivered by CD after 95% gestation (142-144 days). Both ewes and newborn lambs were cared for intensively after the delivery. Ovine uterine anatomy during CD appeared slightly different but comparable to the human uterus. Uterine incisions were mostly performed in the uterine horns, not in the uterine corpus. The ovine uterine wall is thinner than in humans. All ewes survived without any major complications. Seventy-seven (88.5%) out of 87 live-born lambs survived without any complications. The contraction-free ewe constitutes an appropriate and safe model to evaluate anatomical and surgical aspects of CD from a human medical perspective. We present a step-by-step manual for successfully planned cesarean delivery for sheep including the perioperative management illustrated with photographs and a five-minute video. With adequate planning and a reasonable number of staff, it is possible to safeguard both maternal and neonatal survival. This sustainable translational medicine model offers additional potential for the offspring to be used for further research studies (e.g., transgenerational inheritance research).

Uterine scars after caesarean delivery: From histology to the molecular and ultrastructural level

Uterine rupture during a trial of labor after caesarean delivery (CD) is a serious complication for mother and fetus. The lack of knowledge on histological features and molecular pathways of uterine wound healing has hindered research in this area from evolving over time. We analysed collagen content and turnover in uterine scars on a histological, molecular and ultrastructural level. Therefore, tissue samples from the lower uterine segment were obtained during CD from 16 pregnant women with at least one previous CD, from 16 pregnant women without previous CD, and from 16 non-pregnant premenopausal women after hysterectomy for a benign disease. Histomorphometrical collagen quantification showed, that the collagen content of the scar area in uterine wall specimens after previous CD was significantly higher than in the unscarred myometrium of the same women and the control groups. Quantitative real-time PCR of uterine scar tissue from FFPE samples delineated by laser microdissection yielded a significantly higher COL3A1 expression and a significantly lower COL1A2/COL3A1 ratio in scarred uteri than in samples from unscarred uteri. Histological collagen content and the expression of COL1A2 and COL3A1 were positively correlated, while COL1A2/COL3A1 ratio was negatively correlated with the histological collagen content. Transmission electron microscopy revealed a destroyed myometrial ultrastructure in uterine scars with increased collagen density. We conclude that the high collagen content in uterine scars results from an ongoing overexpression of collagen I and III. This is a proof of concept to enable further analyses of specific factors that mediate uterine wound healing.

Intraoperative ultrasound during repeat cesarean delivery facilitates sampling of uterine scar tissue

OBJECTIVES

Histological examination of uterine scars provides insight into uterine wound healing and helps to develop prevention methods of uterine wall rupture after previous uterine surgery. Therefore, exact intraoperative scar identification is needed for specimen collection from the actual scar tissue. The aim of this study was to correlate pre- and intraoperative ultrasound measurements of the lower uterine segment (LUS) with histological findings of scar tissue and to evaluate the relevance of intraoperative ultrasound.

METHODS

In a prospective observational study, preoperative and intraoperative sonographic measurements of the LUS thickness were performed in 33 women with a history of at least one cesarean delivery. Intraoperative ultrasound with a linear transducer placed directly on the uterus identified the scar area and uterotomy was performed 2 cm cranially. Tissue samples were taken after extraction of the fetus, embedded in paraffin wax, and stained according to Gomori Trichrome to identify scar tissue. Collagen content was evaluated with imaging software Fiji (NIH, Bethesda, USA). Preoperative and intraoperative sonographic measurements were correlated with histologic evidence of scar tissue.

RESULTS

Histological evidence of scar tissue was found in 11 out of 33 samples with significantly lower ultrasonographic thickness of the lower uterine segment compared to the other 22 samples, both antepartum (1.4 mm [1.3-1.9] vs. 2.0 mm [1.6-2.6], p=0.03) and intrapartum (1.6 mm [1.3-1.9] vs. 3.7 mm [2.0-4.7], p<0.01). Intraoperative ultrasound had a significantly higher predictive power (AUC difference 0.18 [0.03-0.33], p=0.01).

CONCLUSIONS

Intraoperative sonography identifies the uterine wall area with histologically confirmable scar tissue far better than preoperative sonography.

Risk factors and outcomes associated with type of uterine rupture

PURPOSE

To identify risk factors associated with the occurrence of complete uterine rupture (CUR) in comparison to partial uterine rupture (PUR) to further investigate to what extent a standardized definition is needed and what clinical implications can be drawn.

METHODS

Between 2005 and 2017 cases with CUR and PUR at Charité University Berlin, Germany were retrospectively identified. Demographic, obstetric and outcome variables were analyzed regarding the type of rupture. Binary multivariate regression analysis was conducted to identify risk factors associated with CUR. In addition, the intended route of delivery (trial of labor after cesarean delivery (TOLAC) and elective repeat cesarean delivery (ERCD)), divided according to the type of rupture, was compared.

RESULTS

92 cases with uterine rupture were identified out of a total of 64.063 births (0.14%). Puerperal complications were more frequent in CUR (67.9 versus 41.1%, p = 0.021). Multiparity ≥ 3 was more frequent in CUR (31 versus 10.7%, p = 0.020). Factors increasing the risk for CUR were parity ≥ 3 (OR = 3.8, p = 0.025), previous vaginal birth (OR = 4.4, p = 0.011), TOLAC (OR = 6.5, p < 0.001) and the use of oxytocin (OR = 2.9, p = 0.036). After multivariate analysis, the only independent risk factor associated with CUR was TOLAC (OR = 7.4, p = 0.017).

CONCLUSION

TOLAC is the only independent risk factor for CUR. After optimized antenatal counselling TOLAC and ERCD had comparable short-term maternal and fetal outcomes in a high resource setting. A high number of previous vaginal births does not eliminate the risk of uterine rupture. A clear distinction between CUR and PUR is essential to ensure comparability among studies.