Obstetric hemorrhage: previa, accreta, atony
Why examiners ask this
Hemorrhage is the leading preventable cause of maternal death, and it is a team failure more often than a technical one. Examiners use it to test organization (who do you call, what do you open, in what order), application of knowledge about uterotonics and fibrinogen, and judgment about converting a working neuraxial block to general anesthesia. The planned accreta case also tests preoperative planning, which candidates often underprepare.
The 60-second answer
I treat this as a staged protocol with the obstetric team. I call for help, activate the massive transfusion protocol early, and quantify blood loss rather than estimate it. I get two large-bore IVs, an arterial line when loss is ongoing, and send a CBC, fibrinogen and viscoelastic testing. For atony I escalate uterotonics in sequence: oxytocin, then methylergonovine if she is not hypertensive, carboprost if she is not asthmatic, and misoprostol. I give tranexamic acid 1 g within three hours of birth.1 I transfuse in a ratio close to 1:1:1 and keep fibrinogen above 200 mg/dL, because a level below 200 predicts progression to severe hemorrhage.2 If bleeding continues, I prepare for balloon tamponade, compression sutures, interventional radiology or hysterectomy, and I decide when the neuraxial block is no longer the safe anesthetic.
Decision points and the "why"
- Fibrinogen is the early marker — obstetric coagulopathy is often fibrinogen-driven, especially with abruption and amniotic fluid embolism. I give cryoprecipitate or fibrinogen concentrate guided by viscoelastic testing rather than waiting for a lab value.
- Uterotonic sequence with contraindications — oxytocin infusion first; methylergonovine 0.2 mg IM only if she is normotensive, because it causes severe vasoconstriction and hypertension; carboprost 250 mcg IM is avoided in asthma; misoprostol 600–1000 mcg is an adjunct.3 I state each contraindication as I give each drug.
- Convert to general anesthesia early when unstable — a sympathectomized patient losing blood compensates poorly, and she cannot protect her airway if she becomes obtunded. I convert with ketamine or etomidate and a reduced dose, not propofol at full dose.
- Planned accreta: plan as a vascular case — multidisciplinary team, scheduled delivery at a level III or higher center at about 34 0/7–35 6/7 weeks with massive transfusion capability,4 crossmatched blood in the room, cell salvage, arterial line and large-bore access. Many centers start with a neuraxial technique and convert; I offer a planned general anesthetic when invasion is extensive or a long hysterectomy is likely.
- Cell salvage is acceptable — ACOG/SMFM list it as an option in accreta,4 and amniotic fluid contamination concerns have not been borne out; I use a leukocyte depletion filter and give anti-D if the mother is Rh-negative.
- Keep her warm and ionized calcium normal — hypothermia and citrate-induced hypocalcemia worsen coagulopathy and contractility.
The complication they will inject
After delivery of a placenta accreta, blood loss passes 3 L, the pressure is 70/40 and she becomes confused under the epidural. I tell the room she is in hemorrhagic shock and I am securing the airway. I convert to general anesthesia with a small dose of ketamine and rocuronium by rapid sequence, call for more hands, and run blood through a rapid infuser. I give products by ratio while sending a viscoelastic test and fibrinogen, give calcium chloride for ionized calcium below 1.1 mmol/L, and confirm TXA was given. I tell the obstetricians that if bleeding continues, hysterectomy now is better than more blood. I reassess acid-base, potassium and temperature every 15–30 minutes.
Pitfalls that cost points
- Estimating blood loss visually and under-calling it; young women compensate until they collapse.
- Giving crystalloid in large volume while waiting for blood.
- Giving methylergonovine to a pre-eclamptic patient or carboprost to an asthmatic.
- Forgetting fibrinogen and calcium in the transfusion plan.
- Listing uterotonics without stating who does what in the room.
Rapid-why
Q: Why is fibrinogen higher at baseline in pregnancy? A: Pregnancy is procoagulant; normal fibrinogen is 400–600 mg/dL, so a "normal" lab value of 200 is already a large drop.
Q: When does TXA lose its benefit? A: Starting it more than three hours after birth confers no benefit; the WOMAN trial showed reduced bleeding deaths when given early.1
Q: What risk factor matters most for accreta? A: Placenta previa with prior cesarean; with previa the risk is about 3%, 11%, 40%, 61% and 67% after one through five or more cesareans.4
Q: Why is atony the most common cause? A: The uterus stops bleeding by contracting around spiral arteries; anything that impairs contraction (overdistension, prolonged labor, chorioamnionitis, volatile agents) leaves them open.
Numbers to know
| Item | Value |
|---|---|
| Postpartum hemorrhage | ≥1000 mL cumulative loss or loss with hypovolemia, within 24 h3 |
| Tranexamic acid | 1 g IV at 1 mL/min within 3 h; second 1 g if bleeding continues at 30 min or recurs within 24 h1 |
| Methylergonovine | 0.2 mg IM every 2–4 h; avoid in hypertension or pre-eclampsia3 |
| Carboprost | 250 mcg IM every 15–90 min, max 2 mg (8 doses); caution in asthma5 |
| Fibrinogen target | >200 mg/dL |
| Uterine blood flow at term | ~700 mL/min |
Links
- Massive hemorrhage and transfusion, Uterotonics and tocolytics (coming), dic, Amniotic fluid embolism (coming), Perioperative hypothermia and coagulopathy, The patient who refuses blood (coming)
- ACOG Practice Bulletin on postpartum hemorrhage; ACOG/SMFM obstetric care consensus on placenta accreta spectrum
Sources
- 1.Joint statement of recommendation for the use of tranexamic acid for the treatment of postpartum haemorrhage · FIGO / ICM · figo.org
- 2.Association between fibrinogen levels and severity of postpartum haemorrhage · Colombian Journal of Anesthesiology · elsevier.es
- 3.Postpartum Hemorrhage: Medications to Treat Uterine Atony · The ObG Project, 2022 · obgproject.comSummary drawing on ACOG Practice Bulletin 183.
- 4.Placenta Accreta Spectrum (Obstetric Care Consensus No. 7) · ACOG/SMFM, 2018 · assets.noviams.com
- 5.Hemabate (carboprost tromethamine) prescribing information · Pfizer (FDA labeling) · pfizermedical.com
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.