Clinical overview
Uterine rupture is a full-thickness separation of the uterine wall — myometrium and overlying visceral peritoneum (serosa) — that, when complete, opens the uterine cavity into the peritoneal cavity. It is one of the great intrapartum catastrophes: in a matter of minutes it can exsanguinate the mother and asphyxiate the fetus. Because the fetus may be partly or wholly extruded into the abdomen and the placenta separated from its blood supply, the perinatal mortality of complete rupture is high, and maternal death from haemorrhage remains a real outcome where surgical and blood-bank response is slow. For the South African registrar this is not an abstract examination topic. Obstetric haemorrhage is consistently one of the leading direct causes of maternal death reported by the Saving Mothers / NCCEMD programme, and ruptured uterus sits within that bracket — frequently judged avoidable through earlier recognition of obstructed labour, safer use of uterotonics, and timely transfer between levels of care.
The clinical problem is twofold. First, recognition: classic teaching describes sudden severe pain, cessation of contractions, vaginal bleeding, an abnormal fetal heart rate, loss of station and maternal collapse, but in practice the presentation is often insidious, and an abnormal cardiotocograph (CTG) — particularly new fetal bradycardia — is the single most consistent sign. Second, response: rupture is a "decision-to-delivery in minutes" emergency demanding simultaneous maternal resuscitation, massive-haemorrhage activation and immediate laparotomy. In a country where many women labour in district hospitals without on-site obstetricians, blood banks or theatres, the registrar's job is as much about anticipating the high-risk parturient — the woman with a previous caesarean attempting vaginal birth after caesarean, or the multipara in obstructed or oxytocin-augmented labour — as it is about operating once disaster strikes.
Core knowledge
Definitions and a critical distinction
Two entities must be separated because their significance differs enormously:
- Complete (true) uterine rupture — full-thickness disruption of the uterine wall including the visceral peritoneum, communicating with the peritoneal cavity. The fetus, placenta or both may be wholly or partly extruded. This is the surgical emergency.
- Uterine (scar) dehiscence — a "windowing" or separation of a previous scar in which the visceral peritoneum (and often the fetal membranes) remains intact, with no extrusion and frequently little bleeding. Many dehiscences are asymptomatic and found incidentally at repeat caesarean. They are not equivalent to rupture, though a dehiscence can extend into frank rupture during labour.
This distinction matters for counselling, for VBAC decision-making, and for examination answers — conflating the two is a common error.
Pathophysiology
The pregnant uterus ruptures along a line of mechanical weakness or under a load the wall cannot bear. Two dominant mechanisms:
- Rupture through a previous uterine scar. The commonest setting in modern obstetrics. A previous lower-segment caesarean scar is far more resistant than a classical (upper-segment vertical) scar; the upper segment is the contractile, thick, high-tension part of the uterus and a vertical scar there carries a substantially higher rupture risk, classically quoted in the order of a few percent and high enough that classical scars are a contraindication to planned labour. Other scars carry risk too: previous myomectomy (especially if the cavity was breached), prior rupture or dehiscence repair, cornual/interstitial ectopic resection, and uterine perforation.
- Rupture of an unscarred uterus. Less common but often more devastating, and disproportionately important in low-resource settings. The usual substrate is obstructed labour — cephalopelvic disproportion, malposition or malpresentation, a fetal anomaly, or a pathological retraction (Bandl's) ring — where the lower segment thins and finally tears. Layered on this are inappropriate uterotonic use (oxytocin or, dangerously, misoprostol-driven hyperstimulation), high parity (the multiparous uterus is more fragile), prior instrumentation, fundal pressure, internal podalic version, difficult instrumental delivery, and direct trauma (assault, motor-vehicle crash). Placenta percreta invading through the wall is another mechanism.
The final common path in obstructed labour is worth picturing: the upper segment retracts and shortens while the lower segment passively stretches and thins to accommodate the impacted presenting part. The junction between the two — the physiological retraction ring — rises abnormally high and becomes palpable as Bandl's ring, a late, ominous sign of imminent rupture.