Obstetric Emergencies

In depth

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Maternal physiology that changes ICU care

Cardiac output rises 30–50% through a larger stroke volume and a faster heart rate, vascular resistance falls, and plasma volume grows 40–50%. When Clark 1989 catheterized healthy women at 36–38 weeks and again postpartum, the extra volume sat in a dilated, low-resistance circuit with unchanged filling pressures, but lower oncotic pressure left less margin before pulmonary edema.

Each contraction returns roughly 300–500 mL to the circulation, and output peaks just after delivery, a common time for women with mitral stenosis, pulmonary hypertension or cardiomyopathy to decompensate. From about 20 weeks the supine uterus compresses the vena cava: on MRI at term, supine IVC volume was under a fifth of nonpregnant values, unchanged at 15° of left tilt and much larger at 30° (Higuchi 2015). In Lee 2012, 7% of women lost over 20% of cardiac output with less than 15° of tilt, and neuraxial block, sedation or hemorrhage removes the compensation.

Progesterone raises minute ventilation 30–50%, so PaCO₂ falls to 27–32 mmHg with HCO₃⁻ 18–22 mEq/L and pH 7.40–7.47. A PaCO₂ of 40 in a pregnant asthmatic means she is tiring, and the low bicarbonate buffers acidosis poorly. FRC falls 15–20% while oxygen consumption rises 20–33%, so apnea desaturates her fast. SMFM recommends SpO₂ of 95% or more; WHO's COVID-19 guidance used 92–96%, and some experts accept that range while the fetal tracing is reassuring. The safe ceiling for permissive hypercapnia is unknown.

The airway is edematous and friable: use a 6.0–7.0 mm tube and avoid the nose. Intubation failed in 1 in 390 obstetric general anesthetics, with about one death per 90 failures (Kinsella 2015). OAA/DAS 2015 advises head-up preoxygenation, nasal oxygen and gentle mask ventilation after induction, two intubation attempts at most and an early second-generation supraglottic airway.

Preeclampsia with severe features, eclampsia and HELLP

Preeclampsia starts with an ischemic placenta releasing antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) while placental growth factor (PlGF) falls. The endothelial injury causes vasospasm, capillary leak, platelet consumption and lost cerebral autoregulation. The ICU sees stroke, eclampsia, posterior reversible encephalopathy syndrome (PRES), pulmonary edema, AKI, HELLP, liver hematoma and DIC.

PB 222 gives magnesium 4–6 g IV over 20–30 min, then 1–2 g/h until 24 h after delivery (started before a cesarean and run through it), or 10 g IM then 5 g IM every 4 h without IV access. It is renally cleared: with creatinine 1.0–1.5 mg/dL or urine under 30 mL/h for 4 h, give the full load but 1 g/h, check levels every 4 h, stop above 9.6 mg/dL and restart lower below 8.4. It is contraindicated in myasthenia gravis, prolongs neuromuscular blockade and relaxes the uterus.

Most eclamptic seizures are self-limited: protect her, turn her on her side, oxygenate, then give magnesium to prevent the next (PB 222). Fetal bradycardia during the seizure usually recovers once she is oxygenated, so stabilize her before deciding on delivery. For seizures continuing 20 min after the bolus, or more than two recurrences, PB 222 lists amobarbital, thiopental or phenytoin, with intubation and head imaging. A first seizure beyond 48–72 h postpartum, or one on magnesium, needs other causes excluded.

For sustained control, PB 222 also lists infusions of labetalol 1–2 mg/min or hydralazine 0.5–10 mg/h, and ICUs often use nicardipine. Aim for a safe range, not normal, because placental flow follows maternal pressure: 130–150/80–100 in the 2025 ACOG/NAEMSP guideline, 135/85 in NICE NG133. NSAIDs remain preferred over opioids for postpartum pain (PB 222).

In HELLP, platelets fall about 40% a day, bottom out a mean of 23 h after delivery and exceed 100,000 within 7 days in 90% (PB 222). Check labs at least every 12 h; AST over 2,000 or LDH over 3,000 IU/L signals higher mortality, and worsening after day 4 suggests another diagnosis such as acute fatty liver, TTP or HUS. Steroids are not recommended for HELLP itself (PB 222, NICE NG133). RUQ or shoulder pain with shock suggests a ruptured liver hematoma.

Postpartum hemorrhage: escalation, transfusion and tamponade

With blood volume up 40–50%, BP can hold until 1,000–1,500 mL is lost, so heart rate, measured (weighed) loss and the shock index lead. The obstetric shock index (HR/SBP) is normally 0.7–0.9 (Le Bas 2014); in Nathan 2015, under 0.9 was reassuring and 1.7 or more predicted ICU admission. In the ICU, look for a rising fundus, blood pooled under the hips, a hematoma, or intra-abdominal bleeding after cesarean.

Other uterotonic hazards: long high-dose oxytocin infusions cause water intoxication, methylergonovine with strong CYP3A4 inhibitors risks ergotism, and adjunct misoprostol did not reduce blood loss over 500 mL but caused shivering in 65% (Widmer 2010). TXA works best early: benefit fell about 10% per 15 min of delay and was gone after 3 h (Gayet-Ageron 2018). WHO gives TXA to every woman with PPH within 3 h; ACOG PB 183 says to consider it when initial therapy fails. Prophylactic use has not improved clinical outcomes.

Fibrinogen falls first: in Charbit 2007, 2 g/L (200 mg/dL) or less at the start of PPH predicted severe bleeding with a positive predictive value of 100%. Massive transfusion protocols borrow trauma's high plasma ratios (near 1:1:1) with early cryoprecipitate, and OBS2 (Collins 2017) found no need for fibrinogen replacement above about 2 g/L or a FIBTEM A5 of 12 mm. Keep ionized calcium normal, keep her warm and correct acidosis.

Intrauterine tamponade buys time: a Bakri balloon (up to 500 mL of saline) or the Jada suction device, which controlled bleeding in 94% within a median 3 min in a single-arm study (PEARLE, D'Alton 2020). Record fill volume, measure drain output hourly, watch fundal height (a rising fundus means concealed bleeding), keep a urinary catheter, and leave removal to obstetrics. Next come embolization, compression sutures, ligation and hysterectomy. With previa, accreta risk was 3%, 11%, 40% and 61% at the first to fourth cesarean (Silver 2006); the plan is cesarean hysterectomy with the placenta left in place at a level III or IV center (ACOG/SMFM OCC 7).

Amniotic fluid embolism

AFE is sudden cardiorespiratory collapse in labor or within 30 min of placental delivery, with overt DIC and no fever; no test confirms it (SMFM 2016). It appears to be triggered by trophoblast or other fetal material entering the maternal circulation, not by fluid or embolism: acute pulmonary hypertension and right ventricular failure come first, then left ventricular failure, with DIC in more than 80%. Incidence is about 2–6 per 100,000 births with 20–40% case fatality (SMFM 2026); US risk factors were age over 35, previa and cesarean (Abenhaim 2008). SMFM's 2026 checklist:

• No ROSC by 4 min: deliver where she lies; manual left uterine displacement and a timekeeper during CPR
• Remove fetal monitors when CPR starts
• Massive transfusion early, cryoprecipitate over plasma to limit volume; TXA 1 g IV over 10 min; uterotonics
• Right heart failure: echo, 500 mL boluses with reassessment, norepinephrine, adding dobutamine 2.5–5 or milrinone 0.25–0.75 mcg/kg/min
• Inhaled nitric oxide 5–40 ppm or epoprostenol; VA-ECMO if refractory (72% survival in 79 reported cases)

Peripartum cardiomyopathy

PPCM is heart failure with LVEF under 45% late in pregnancy or in the months after delivery, with no other cause (ESC Heart Failure Association). It complicated 1 in 968 US live births in 2004–2011 (Kolte 2014); risks include Black race, older age, multiple gestation and preeclampsia, present in 22% (Bello 2013). Prolactin cleaved into a cardiotoxic fragment is one mechanism, and 15% carry a truncating cardiomyopathy gene variant, mostly titin (Ware 2016). Symptoms mimic late pregnancy, so orthopnea, persistent tachycardia or hypoxemia should prompt a natriuretic peptide, ECG and echocardiogram (HFA 2019).

European guidance adds bromocriptine (2.5 mg daily for 1 week; when severe, 2.5 mg twice daily for 2 weeks, then daily for 6 weeks) with at least prophylactic anticoagulation: in Hilfiker-Kleiner 2017 (63 women, no placebo arm), both durations raised LVEF from about 28% to 50%. US practice varies. In shock, HFA 2019 avoids catecholamines where possible after all 7 women given dobutamine in one series needed transplant or LVAD (Stapel 2017), favoring levosimendan (not available in the US) and early mechanical support; US centers often use dobutamine or milrinone.

In IPAC (McNamara 2015), 72% reached LVEF 50% or more by 12 months, but 13% died, needed transplant or LVAD, or stayed under 35%; none with both LVEF under 30% and LVEDD 6.0 cm or more recovered. A wearable defibrillator bridges the recovery months (HFA 2019). A later pregnancy carried 19% mortality if LV function had not normalized, against 0% if it had (Elkayam 2001).

Sepsis and venous thromboembolism

Sepsis complicates about 1 in 1,000 pregnancies and caused 24% of in-hospital maternal deaths (Bauer and Pacheco 2025). Most sources are genitourinary (intraamniotic infection, endometritis, pyelonephritis), then pneumonia, wounds and necrotizing infection; group A streptococcus can reach toxic shock within hours. Normal pregnancy blurs SIRS and SOFA, and qSOFA found only 36–50% of cases, so use maternal early warning criteria and treat unexplained organ dysfunction with infection as sepsis, fever or not (SMFM #47).

SMFM #47: antibiotics within 1 h, cultures, lactate, source control, 1–2 L of crystalloid, norepinephrine first, and no delivery for sepsis alone. Vasopressin at a fixed 0.03 units/min is a reasonable second pressor, and stress-dose hydrocortisone is held while antenatal steroids are given (Bauer and Pacheco 2025).

VTE risk is 4–5 times that of nonpregnant women, and VTE causes 9.3% of US maternal deaths (ACOG PB 196); postpartum incidence was 5 times, and PE 15 times, the antepartum rate (Heit 2005). DVT is left-sided in 88% and often iliofemoral (Chan 2010), so image proximal and iliac veins. The pregnancy-adapted YEARS algorithm (Artemis, van der Pol 2019) scans symptomatic legs first, then rules out PE with D-dimer under 1,000 ng/mL and no YEARS item (DVT signs, hemoptysis, PE most likely), or under 500 with any item; it avoided CT in 39% with 0.21% VTE at 3 months. Fetal radiation from CT angiography or V/Q is far below harmful levels (ACOG CO 723).

Treat with LMWH (enoxaparin 1 mg/kg every 12 h) or UFH; warfarin and DOACs are avoided (PB 196), and UFH is often substituted near term. Neuraxial block waits 12 h after prophylactic and 24 h after therapeutic LMWH, which restarts 12 or 24 h after the puncture and 4 h after catheter removal (SOAP, ASRA). Thrombolysis for massive PE gave 94% survival, but major bleeding was 17.5% antepartum and 58% postpartum (Martillotti 2017). RCOG advises anticoagulation for at least 6 weeks postpartum and 3 months in total.

Maternal cardiac arrest and resuscitative delivery

Arrest complicated 1 in 12,000 US delivery admissions, mostly from hemorrhage, heart failure, AFE and sepsis, and 58.9% survived to discharge (Mhyre 2014). AHA's BEAU-CHOPS covers causes: bleeding, embolism, anesthetic complications, uterine atony, cardiac disease, hypertensive disorders, other H's and T's, placental abruption or previa, sepsis; add magnesium toxicity.

Compression rate and depth, drug doses and defibrillation energies are unchanged; mechanics change. Manual left uterine displacement avoids the force lost with tilt (27° gave 80% of supine force in Rees 1988). AHA 2025 adds an early expert airway, access above the diaphragm, stopping magnesium and giving calcium, removing fetal monitors, and ECPR as reasonable.

Resuscitative delivery is for the mother: with the fundus at or above the umbilicus, prepare from recognition and deliver by 5 min without ROSC, where she arrested (AHA 2025). The evidence is case reports: delivery preceded return of circulation in 12 of 18 (Katz 2005), and delivery within 10 min was associated with better maternal outcome, OR 7.42 (Einav 2012).

Drugs in pregnancy in the ICU

Maternal need comes first, and most ICU drugs are usable. The FDA's 2015 Pregnancy and Lactation Labeling Rule replaced the A–X letter categories with narrative summaries, so check specific data, and LactMed for breastfeeding.

Betamethasone (12 mg IM, two doses 24 h apart) for likely delivery before 34 weeks raises glucose and WBC for days, mimicking infection. Magnesium before 32 weeks cut moderate or severe cerebral palsy from 3.5% to 1.9%, a secondary outcome (BEAM, Rouse 2008). Rho(D) immune globulin 300 mcg covers 30 mL of fetal whole blood. Terbutaline carries an FDA boxed warning against tocolysis beyond 48–72 h.

Fetal monitoring basics for the ICU nurse

Uterine blood flow lacks autoregulation, so the fetal heart rate reports maternal perfusion: hypotension, hypoxemia, acidosis, hypothermia and seizures show in the tracing, often first. Once neonatal resuscitation would be offered, monitoring is planned with obstetrics and the family (Bauer and Pacheco 2025), and a labor and delivery nurse helps read continuous tracings.

Category I (baseline 110–160, moderate variability, no late or variable decelerations) is normal. Category III (absent variability with recurrent late or variable decelerations or bradycardia, or a sinusoidal pattern) needs immediate obstetric evaluation. Category II is everything else.

Intrauterine resuscitation is maternal resuscitation: reposition, treat hypotension, correct hypoxemia and acidosis, stop oxytocin for more than 5 contractions in 10 min averaged over 30 min, and call obstetrics. Routine oxygen for a well-oxygenated mother did not improve cord pH across 16 trials (Raghuraman 2021). Compare the tracing with her pulse oximeter to be sure it is fetal, not maternal.

Exam pearls

• Pregnancy ABG: compensated respiratory alkalosis, PaCO₂ 27–32; a PaCO₂ of 40 signals impending respiratory failure
• Cardiac output up 30–50%, SVR down, CVP and PCWP unchanged; low oncotic pressure invites pulmonary edema
• From 20 weeks, avoid supine; during CPR, manual left uterine displacement
• Magnesium prevents seizures, not hypertension; toxicity antidote is calcium gluconate 1 g IV
• Treat BP ≥160/110 lasting 15 min within 30–60 min; systolic pressure predicts stroke
• HELLP: LDH ≥600, AST and ALT over twice normal, platelets under 100,000; can start after delivery
• TXA 1 g IV within 3 h of birth; fibrinogen ≤200 mg/dL predicts severe PPH
• AFE: hypoxemia, hypotension or arrest, and DIC in labor or within 30 min of placental delivery
• PPCM: LVEF under 45% late in pregnancy or months after; no ACE inhibitor, ARB or warfarin before delivery
• Resuscitative delivery: prepare at recognition, deliver by 5 min without ROSC, where she arrested