Repeat cesarean delivery with hysterectomy: A sheep model to examine uterine scars

Cesarean delivery (CD) is one of the most common surgical procedures worldwide, with rising rates leading to an increasing impact of complications, such as uterine rupture during a trial of labor in a subsequent pregnancy. To date, only little information on uterine wound healing is available. The current challenge is to establish a suitable model and to define quantifiable outcome parameters of uterine scar tissue with the aim of comparing the effect of different surgical techniques on uterine scarring. This study presents a sheep model to examine the effects of different hysterotomy closure techniques. 48 merino ewes underwent planned cesarean delivery. After one year, 40 ewes were mated again following estrus synchronization and received planned repeat CD with peripartum supracervical hysterectomy and sampling of uterine scar tissue without any major complications. Survival rates at repeat CD were 95.0% and 91.4% for ewes and lambs respectively. Due to placement of non-absorbable sutures around the hysterotomy closure during the first CD, all scarred uterine wall segments could be identified. 16/80 (20%) uterine scars showed dehiscences with a macroscopic thinning of the uterine wall. A full-thickness uterine rupture was not found. Gomori trichrome staining was used to assess the collagen content histomorphometrically. It revealed a markedly scarred uterine wall. This translational model can be used to evaluate intraoperative approaches to optimize uterine wound healing, such as suturing techniques, pharmacological agents or biomaterials, with the aim of reducing the risk of uterine rupture in humans and improving maternal outcomes in pregnancies after previous CD. Lay summary: Cesarean delivery is one of the most common operations worldwide. After a cesarean, a scar remains on the uterus. This scar may not heal properly leading to the risk of serious complications in a subsequent pregnancy, such as uterine rupture. Despite this risk, very little is known about how the uterine wall heals after surgery, because suitable research models are scarce. This study shows that sheep can be used as a model to study uterine scar healing. A planned cesarean delivery was performed in sheep. Sheep were mated again and at the next planned cesarean, the uterus was removed and tissue from the scar was collected. The scars could be clearly identified and some showed thinning similar to what is seen in humans. Microscopic analysis confirmed scar formation. This model will help researchers test new ways to improve uterine healing and make pregnancies after cesarean delivery safer.