Residency · Residency · Obstetrics Gynecology
Obstetric Emergencies: Cord Prolapse, Uterine Rupture, and Amniotic Fluid Embolism
Umbilical Cord Prolapse
Definition and Types
Overt prolapse occurs when the umbilical cord precedes the presenting part through the cervix into the vagina or beyond the introitus. Occult prolapse refers to the cord lying alongside the presenting part but not past the cervix, which may cause variable decelerations without the cord being visible. Funic presentation describes a cord positioned below the presenting part with the membranes still intact. The overall incidence is 0.1 to 0.6% of deliveries.
Risk Factors
Risk factors include artificial rupture of membranes with an unengaged presenting part, polyhydramnios, malpresentation (transverse lie, breech, or oblique), premature rupture of membranes with a preterm fetus, multiple gestation (particularly the second twin), a long umbilical cord, pelvic tumors preventing engagement, and grand multiparity.
Diagnosis
Cord prolapse is diagnosed by palpation of a pulsatile cord on vaginal examination after rupture of membranes, by sudden severe variable or prolonged decelerations on the fetal heart rate tracing immediately after membrane rupture, or by visualization of the cord at the introitus.
Management
Upon recognition, an emergency cesarean delivery is called. The examiner's hand is placed in the vagina to elevate the presenting part off the cord, and no attempt should be made to replace the cord into the uterus. The patient is placed in a steep Trendelenburg or knee-chest position. The bladder is filled with 500 to 700 mL of saline via a Foley catheter, which pushes the presenting part upward. The cord should not be handled, as manipulation causes vasospasm. A tocolytic such as terbutaline 0.25 mg subcutaneously is administered to reduce contractions. Delivery should occur by emergent cesarean within minutes, with a decision-to-incision time ideally less than 10 minutes. If the patient is fully dilated with the vertex at the perineum, operative vaginal delivery may be faster. The neonatal team should be present for delivery.
<image>Management algorithm for umbilical cord prolapse showing the sequence: recognition of prolapse on exam, immediate manual elevation of presenting part, knee-chest or Trendelenburg positioning, bladder filling with saline via Foley catheter, and emergent cesarean delivery</image>
Uterine Rupture
Definition
Uterine rupture is the complete disruption of all layers of the uterine wall including the serosa. Dehiscence, or incomplete rupture, refers to separation of a prior uterine scar without serosal disruption and without significant clinical consequence. Dehiscence is often an incidental finding.
Incidence
The risk of rupture during TOLAC with a prior low transverse cesarean scar is 0.5 to 0.9%. With a prior classical (vertical) cesarean scar, the risk rises to 4 to 9%, which is why classical scars are a contraindication to trial of labor. Prior myomectomy entering the uterine cavity carries a variable risk estimated at 0.5 to 2%. Rupture of an unscarred uterus is extremely rare, occurring in 0.01 to 0.05% of deliveries.
Risk Factors
Risk factors include prior uterine surgery (cesarean, myomectomy, or cornual resection), induction or augmentation with oxytocin or prostaglandins, a short interpregnancy interval of less than 18 to 24 months from the prior cesarean, single-layer uterine closure at the prior cesarean, grand multiparity, uterine anomalies, excessive uterine distension, and obstructed labor.
Clinical Presentation
The classic triad consists of fetal heart rate abnormality (the most reliable sign), abdominal pain, and vaginal bleeding. Sudden prolonged fetal bradycardia is the most common initial presentation. Other findings include loss of the uterine contraction pattern, loss of fetal station, maternal tachycardia and hypotension, palpation of fetal parts through the abdominal wall, hematuria when the bladder is involved, and shoulder tip pain from hemoperitoneum irritating the diaphragm.
Management
Management requires emergent laparotomy and cesarean delivery. The decision between uterine repair and hysterectomy depends on the extent and location of the rupture, the patient's hemodynamic stability, her desire for future fertility, and the surgeon's expertise. Most low-transverse scar ruptures can be repaired primarily. Massive hemorrhage may necessitate hysterectomy. A broad ligament hematoma may involve the uterine artery and requires careful dissection. Bladder injury must be assessed and repaired if present.
<image>Intraoperative illustration showing types of uterine rupture: complete rupture through a prior low transverse scar with fetal parts visible through the defect, compared with uterine dehiscence where the serosa remains intact but the myometrium has separated along the prior incision line</image>
Amniotic Fluid Embolism (AFE)
Pathophysiology
Amniotic fluid embolism was previously thought to result from mechanical obstruction of the pulmonary vasculature by amniotic fluid debris. It is now understood as an anaphylactoid or immune-mediated response to fetal antigens entering the maternal circulation, which has led to the proposed renaming as "anaphylactoid syndrome of pregnancy." The condition triggers a massive inflammatory cascade with complement activation, leading to cardiovascular collapse and disseminated intravascular coagulation.
Incidence and Mortality
AFE is rare, occurring in 1 to 12 per 100,000 deliveries. Mortality remains 20 to 60%, though it has improved with modern critical care. AFE accounts for 5 to 15% of maternal deaths in developed countries, and survivors may have significant neurologic morbidity.
Risk Factors
No reliably predictive risk factors exist. Associations, though not causative, include advanced maternal age, multiparity, cesarean delivery, instrumental delivery, placenta previa, abruption, eclampsia, induction of labor, and polyhydramnios. The condition cannot be predicted or prevented.
Clinical Presentation
AFE presents with acute onset during labor, delivery, or the immediate postpartum period, typically within 30 minutes. Phase 1 involves cardiovascular collapse with sudden profound hypotension, acute respiratory distress and hypoxia progressing to respiratory failure, altered mental status or seizures, cardiac arrest (pulseless electrical activity or ventricular fibrillation), and right heart failure from acute pulmonary hypertension. Phase 2 involves coagulopathy, with massive DIC developing in 83% of patients who survive phase 1. This manifests as uncontrollable hemorrhage from all sites with consumptive coagulopathy characterized by low fibrinogen, elevated D-dimer, and thrombocytopenia.
| Feature | Cord Prolapse | Uterine Rupture | Amniotic Fluid Embolism |
|---|---|---|---|
| Incidence | 0.1-0.6% | 0.5-0.9% (scarred uterus) | 1-12 per 100,000 |
| Mortality | Low (with prompt delivery) | Fetal 5-10%; maternal rare | 20-60% |
| Hallmark finding | Palpable pulsatile cord | Sudden fetal bradycardia | Cardiovascular collapse + DIC |
| Key initial action | Elevate presenting part | Emergent laparotomy | Supportive resuscitation (ACLS) |
| Target delivery time | <10 minutes | As fast as possible | Perimortem cesarean by 5 minutes if arrest |
Diagnosis
AFE is a clinical diagnosis of exclusion with no confirmatory laboratory test. The classic triad of hypotension, hypoxia, and coagulopathy occurring abruptly during labor or delivery is the hallmark. The previously used histologic finding of fetal squamous cells in the pulmonary vasculature is now known to be neither sensitive nor specific. The differential diagnosis includes pulmonary embolism, anaphylaxis, sepsis, myocardial infarction, abruption with DIC, and high spinal block.
Management
Treatment is supportive and resuscitative, as no specific therapy exists. Airway management involves early intubation with high FiO2. Mechanical ventilation with a lung-protective strategy is provided. Circulation is supported with aggressive volume resuscitation using crystalloid and blood products, vasopressors (norepinephrine, vasopressin, or phenylephrine), and inotropes such as dobutamine or milrinone for cardiogenic shock. ECMO may be considered if available and the patient is not responding to conventional support. DIC is managed with massive transfusion protocol activation using a 1:1:1 ratio, cryoprecipitate to maintain fibrinogen above 200 mg/dL, platelet transfusion, and avoidance of heparin. If the patient has not yet delivered, emergent perimortem cesarean should be initiated within 4 to 5 minutes of cardiac arrest. After delivery, hemorrhage is treated aggressively, and hysterectomy may be necessary for refractory uterine atony or coagulopathy. Multidisciplinary ICU care involving maternal-fetal medicine, anesthesiology, critical care, and hematology is essential.
<image>Pathophysiology diagram of amniotic fluid embolism showing fetal antigens entering maternal circulation through disrupted uteroplacental interface, triggering complement activation and anaphylactoid response, leading to two phases: Phase 1 with acute pulmonary hypertension, right heart failure, and cardiovascular collapse, and Phase 2 with massive DIC and hemorrhage</image>
Team Communication in Obstetric Emergencies
Principles
Closed-loop communication requires the sender to give an order, the receiver to repeat it back, and the sender to confirm. The SBAR format (Situation, Background, Assessment, Recommendation) is used for handoffs and escalation. A designated team leader directs the response without performing procedures. A time-keeper announces elapsed time, and a scribe handles documentation. Debriefing is conducted after every emergency event, with a hot debrief immediately and a cold debrief within 1 to 2 weeks.
Simulation Training
Regular simulation drills, at least quarterly, should cover cord prolapse, shoulder dystocia, eclampsia, postpartum hemorrhage, amniotic fluid embolism, and maternal cardiac arrest. Interdisciplinary involvement is essential, including nurses, midwives, anesthesiologists, obstetricians, and neonatologists. Standardized checklists and cognitive aids support performance. Debriefing focuses on systems improvement rather than individual blame.
Clinical Pearls
In cord prolapse, the examiner's hand should continuously elevate the presenting part until delivery. No attempt should be made to replace the cord into the uterus.
Bladder filling with 500 to 700 mL of saline via a Foley catheter is a critical temporizing maneuver for cord prolapse when the operating room is not immediately available.
The most common and earliest sign of uterine rupture is a fetal heart rate abnormality, typically sudden prolonged bradycardia.
Loss of station on vaginal examination during labor should raise immediate suspicion for uterine rupture.
AFE is a clinical diagnosis of exclusion. Resuscitation should not be delayed while waiting for confirmatory tests that do not exist.
Perimortem cesarean should be initiated within 4 minutes of maternal cardiac arrest and completed by 5 minutes to optimize both maternal and neonatal survival.
Every delivery unit should have emergency response protocols posted and regularly rehearsed.
<image>Emergency response timeline for maternal cardiac arrest showing minute-by-minute actions: minute 0 - call code and begin CPR with left uterine displacement, minute 1 - establish IV access and administer epinephrine, minute 2-3 - assess reversible causes (4 H's and 4 T's), minute 4 - begin perimortem cesarean if no ROSC, minute 5 - deliver infant, continue maternal resuscitation</image>
References
- ACOG Practice Bulletin No. 202: Gestational Hypertension and Preeclampsia (2019) -- sections on emergency response
- Holbrook BD, Bhargava A. Umbilical cord prolapse. Obstet Gynecol Clin North Am. 2020;47(3):423-436
- Guise JM et al. Uterine rupture: current concepts. Am J Obstet Gynecol. 2010;202(4):e1-e6
- Clark SL. Amniotic fluid embolism. Obstet Gynecol. 2014;123:337-348
- Society for Maternal-Fetal Medicine. AFE Clinical Guidance (2016, updated 2023)
- ACOG Committee Opinion No. 590: Preparing for clinical emergencies in obstetrics and gynecology (2014)
- Lipman SS et al. AHA Scientific Statement: Cardiac arrest in pregnancy. Circulation. 2023
