Bleeding after about 20 weeks is an obstetric emergency until proven otherwise. Near term, about 500–900 mL of blood flows to the uterus every minute (10–15% of cardiac output), so hemorrhage can become life-threatening within minutes. The main causes are placenta previa, placental abruption, vasa previa, and uterine rupture; placenta accreta spectrum is a closely linked condition. Minor causes include cervical changes of labor ("bloody show"), cervicitis, and cervical polyps.

Placenta previa

• The placenta lies over the internal cervical os. When the placental edge is within 2 cm of the os but does not cover it, the current term is low-lying placenta (older terms "marginal" and "partial" previa are no longer recommended)
• As the lower uterine segment stretches and the cervix changes, placental attachments tear → painless, bright red bleeding, often a first "sentinel" episode in the late second or third trimester
• Most previas seen on the mid-pregnancy ultrasound resolve as the uterus grows; follow-up ultrasound is done at about 32 weeks
• Risk factors: previous cesarean birth and other uterine surgery, multiparity, advanced maternal age, smoking, multiple gestation, IVF, previous previa, cocaine use
• The placenta occupies the lower segment, so the fetus is often in an abnormal lie or presentation (breech, transverse)

Placental abruption

• Premature separation of a normally implanted placenta before birth → bleeding into the decidua behind the placenta, loss of placental exchange surface, fetal hypoxia
• Bleeding may be visible (dark red) or concealed behind the placenta (no external blood despite major loss)
• Blood in the myometrium can produce a bruised, bluish Couvelaire uterus that contracts poorly
• Release of tissue factor consumes clotting factors → disseminated intravascular coagulation (DIC)
• Risk factors: hypertension and preeclampsia (the strongest), previous abruption, abdominal trauma (motor vehicle crash, intimate partner violence), cocaine and tobacco, preterm prelabor rupture of membranes, sudden uterine decompression (rupture of membranes with polyhydramnios, after birth of a first twin), thrombophilia, advanced maternal age

Comparison

Vasa previa — unprotected fetal vessels run through the membranes over or near the cervix. When membranes rupture, the vessels tear → painless bleeding followed by sudden fetal bradycardia. The blood lost is fetal, so a small volume can kill the fetus.

Uterine rupture — a tear through the uterine wall, most often at a previous cesarean scar. Risk factors: prior cesarean (especially a classical/vertical fundal incision), other uterine surgery (myomectomy entering the cavity), oxytocin or prostaglandin use in a scarred uterus, obstructed labor, trauma, uterine overdistension, uterine anomalies. A history of spontaneous early pregnancy loss is not a risk factor.

Placenta accreta spectrum (PAS) — the placenta invades abnormally into (accreta), into the muscle of (increta), or through (percreta) the uterine wall and cannot separate after birth → massive hemorrhage. The strongest risk is placenta previa with previous cesarean birth; risk climbs with each cesarean.

• Maternal hemodynamics first: heart rate, BP, respiratory rate, SpO₂, skin color and temperature, level of consciousness, urine output; a young healthy client may keep a normal BP until large blood loss — tachycardia is the early sign
• Bleeding: onset, amount (pad weight), color, clots; relationship to trauma, intercourse, or membrane rupture
• Pain and uterine tone, tenderness, and contractions; mark the fundal height and measure abdominal girth to detect concealed bleeding (rising fundus)
• Continuous electronic fetal monitoring — baseline, variability, accelerations, decelerations
• Gestational age, previous cesarean, blood type and Rh, prior ultrasounds (placental location)

• Ultrasound — transvaginal ultrasound is safe and most accurate for placental location; it will not provoke bleeding. Ultrasound often misses abruption, which is a clinical diagnosis
• CBC, fibrinogen (a level below about 200 mg/dL (2 g/L) predicts severe hemorrhage), PT/INR, aPTT, platelets, D-dimer — screen for DIC
• Type and crossmatch; blood type, Rh, and antibody screen
• Kleihauer–Betke or flow cytometry — measures fetal blood in maternal circulation (RhIG dosing)
• Doppler or MRI for suspected placenta accreta spectrum; prenatal ultrasound with color Doppler for vasa previa

Placenta previa

• Active bleeding: hospitalize; stabilize; transfuse as needed; continuous fetal monitoring
• Antenatal corticosteroids (e.g., betamethasone 12 mg IM, 2 doses 24 hours apart) if delivery is likely between 24 0/7 and 33 6/7 weeks (considered in selected cases outside this range); magnesium sulfate for fetal neuroprotection if birth before 32 weeks is imminent
• RhIG for Rh-negative unsensitized clients after a bleeding episode
• Stable clients with resolved bleeding may be managed as outpatients if they live close to the hospital and have transport; strict bed rest is not required — pelvic rest is advised
• Planned cesarean birth at 36 0/7–37 6/7 weeks for uncomplicated previa; 34 0/7–35 6/7 weeks for suspected placenta accreta spectrum (planned cesarean hysterectomy at a specialist center); emergency cesarean for uncontrollable bleeding or fetal compromise at any gestational age
• A low-lying placenta may allow a trial of labor in selected cases

Placental abruption

• Management depends on severity, maternal and fetal condition, and gestational age
• Mild, stable, preterm, reassuring fetal testing → close inpatient observation, corticosteroids
• Maternal or fetal compromise → prompt birth: cesarean if the fetus is alive and compromised; vaginal birth is often preferred when the fetus has died and the client is stable
• Tocolytics are generally avoided when abruption is suspected
• Massive transfusion protocol for severe hemorrhage and DIC (red cells, plasma, platelets, cryoprecipitate/fibrinogen)

Vasa previa — prenatal diagnosis; hospitalization around 30–34 weeks in many centers; planned cesarean at 34 0/7–35 6/7 weeks (SMFM/ACOG) before membranes rupture; immediate cesarean if bleeding with rupture of membranes.

Uterine rupture — immediate laparotomy/cesarean, repair or hysterectomy, resuscitation.

Trial of labor after cesarean (TOLAC) — appropriate for most clients with one or two previous low transverse incisions; contraindicated after a classical incision or previous rupture. It must take place in a facility able to perform emergency cesarean immediately. Misoprostol is not used for cervical ripening in clients with a uterine scar.

Listed in priority order.

1. Maternal ABCs and circulation
   • Call for help; two large-bore IVs; warmed isotonic crystalloids and blood products as ordered; oxygen if hypoxic
   • Vital signs every 5–15 minutes; indwelling catheter with hourly urine output (keep ≥ 30 mL/h)
   • Lateral position (left uterine displacement) to improve venous return and placental perfusion
2. No vaginal or rectal examinations until placenta previa is excluded by ultrasound; nothing in the vagina
3. Continuous fetal monitoring — report abnormal patterns immediately; continuous monitoring of FHR patterns is the most direct way to track fetal oxygenation during bleeding
4. Labs and blood — send CBC, coagulation studies, fibrinogen, type and crossmatch; watch for DIC (oozing from IV sites, gums, petechiae, hematuria)
5. Prepare for emergency cesarean — consent, NPO, neonatal team present
6. Monitor concealed bleeding — fundal height marking, abdominal girth, increasing pain and uterine tone
7. After birth — previa: high risk of postpartum hemorrhage because the lower uterine segment contracts poorly at the placental site; monitor fundus, lochia, and vital signs closely; give uterotonics as ordered. Abruption: Couvelaire uterus and DIC increase hemorrhage risk
8. Emotional support — explain events calmly, keep the support person informed, support grief if the fetus dies

Placenta previa (outpatient)

• Pelvic rest — no intercourse, tampons, or douching
• Avoid heavy lifting and strenuous exercise
• Stay near the hospital with transport available at all times; bleeding can recur suddenly and heavily
• Come immediately for any bleeding, contractions, fluid leakage, or decreased fetal movement
• Count fetal movements as instructed

Abruption prevention and warning signs

• Stop smoking and avoid cocaine; control blood pressure
• Always wear a seat belt correctly (lap belt below the abdomen)
• After any abdominal trauma, even minor, seek evaluation — after viability this usually means continuous fetal and contraction monitoring for at least 4 hours, and RhIG if Rh-negative
• Report sudden abdominal pain, a hard uterus, bleeding, or reduced fetal movement

Previous cesarean — discuss TOLAC vs repeat cesarean; if choosing TOLAC, go to the hospital early in labor.

• Previa = painless bright red bleeding, soft uterus; abruption = painful bleeding (may be concealed), tender board-like uterus, fetal distress
• Never perform a vaginal exam until previa is ruled out; transvaginal ultrasound is safe
• Previous cesarean is the major risk factor for previa and placenta accreta spectrum
• Hypertension/preeclampsia, trauma, cocaine, smoking → abruption; abruption → DIC, Couvelaire uterus
• Priority: maternal hemodynamics (vital signs, IV access, blood) and continuous fetal monitoring
• Tachycardia is an early sign of hemorrhage; keep urine output ≥ 30 mL/h
• Previa birth by cesarean at 36 0/7–37 6/7 weeks; PAS at 34 0/7–35 6/7 weeks
• Previa → high risk of postpartum hemorrhage (poor lower-segment contraction)
• Vasa previa = painless bleeding at membrane rupture + fetal bradycardia (fetal blood loss)
• Uterine rupture: most common sign is an abnormal FHR; TOLAC only where immediate cesarean is possible; classical scar contraindicates TOLAC
• Give RhIG to Rh-negative unsensitized clients after bleeding