Bandl's ring

Bandl's ring (also known as pathological retraction ring) is the abnormal junction between the two segments of the human uterus, which is a late sign associated with obstructed labor.^[1] Prior to the onset of labour, the junction between the lower and upper uterine segments is a slightly thickened ring. In abnormal and obstructed labours, after the cervix has reached full dilatation further contractions cause the upper uterine segment muscle fibres myometrium to shorten, so that the actively contracting upper segment becomes thicker and shorter. The ridge of the pathological ring of Bandl's can be felt or seen rising as far up as the umbilicus. The lower segment becomes stretched and thinner and if neglected may lead to uterine rupture.

References

1. Turrentine MA, Andres RL. (Jan 1994). "Recurrent Bandl's ring as an etiology for failed vaginal birth after cesarean section". Am J Perinatol. 11 (1): 65–6. doi:10.1055/s-2007-994539. PMID 8155216.