Peek A Boo! Peeping through the scar: Amniotic sac and fetal protrusion through a dehiscent uterine wall

Abstract

Introduction:

Lower uterine segment (LUS) dehiscence is a partial disruption of a previous uterine scar in which the myometrium is compromised while the serosa remains intact. It is often detected incidentally during repeat cesarean sections and is rarely recognized in early pregnancy. Although frequently asymptomatic, it carries a significant risk of progression to complete uterine rupture, which involves a full-thickness tear of the uterine wall and is associated with severe maternal and fetal morbidity. Prior cesarean delivery is the most important risk factor.

Case history:

A 32-year-old gravida 2 para 1 woman with previous cesarean section and gestational hypertension presented at 13 weeks with abdominal pain and vaginal bleeding. Ultrasound at a referring facility showed intrauterine fetal demise for which dilatation and curettage (D&C) was performed. Follow-up ultrasound revealed an amniotic sac–like structure protruding through a 6.6 mm defect at the previous scar, with a macerated fetus partially visible. Emergency laparotomy confirmed partial scar dehiscence with a 2 × 2 cm defect, and fetal parts, placenta, and clots were removed, followed by repair of the uterine defect.

Discussion:

Uterine scar dehiscence is a rare but serious complication, mostly seen in patients with prior uterine surgery, particularly cesarean deliveries, and often asymptomatic until progression. Weakening of the myometrium can lead to separation while the serosa remains intact. In this case, transvaginal ultrasound identified amniotic sac extrusion through the scar, enabling timely surgical repair to prevent complete rupture and improve maternal-fetal outcomes.

Conclusion:

This case highlights the importance of ultrasound in early pregnancy for evaluating scar integrity in women with previous cesarean sections. Assessment should extend beyond measuring lower uterine segment thickness to actively identify myometrial discontinuity and herniation of gestational contents. Early recognition enables timely intervention, prevents catastrophic uterine rupture, and improves maternal outcomes.