Oxygen-carrying reserve
Plasma volume expands more than red-cell mass, producing physiologic dilutional anemia. Interpret against gestational age, symptoms, bleeding, and prior values.
Chapter11
Assessment
Laboratory and Diagnostic Assessment
Educational use onlyThis chapter supports certification preparation and transport reasoning. Follow local protocols, scope of practice, ordering-provider instructions, and medical direction.
Learning objectives
After completing this chapter, you should be able to interpret pregnancy-specific laboratory trends, recognize high-risk patterns, identify preanalytic limitations, use focused diagnostic testing within scope, and communicate how results change the transport plan.
Use the five-part diagnostic lens
1
Question
What clinical decision will this test inform?
2
Pregnancy baseline
Is the expected normal range different?
3
Trend
Is the value rising, falling, or stable?
4
Timing
Was it drawn before or after treatment or bleeding?
5
Action
Does it change treatment, destination, or urgency?
Opening transport scenario
A 31-year-old patient at 35 weeks is transferred for severe hypertension and right-upper-quadrant pain. Platelets have fallen from 168,000 to 92,000/µL in six hours, creatinine has risen from 0.6 to 1.2 mg/dL, AST is more than twice normal, and the fetal tracing is worsening. No single number tells the whole story. The trend shows evolving multisystem disease and a narrowing margin for safe transport.
Mother–fetus connectionMaternal laboratory deterioration may identify declining placental perfusion and fetal risk before profound maternal hypotension or altered mental status appears.
1. Complete blood count
Inflammation in context
Pregnancy and labor can raise the white count. Leukocytosis alone does not diagnose infection; fever, source, differential, lactate, perfusion, and trend matter.
Hemostasis and severe disease
Mild gestational thrombocytopenia is common, but a rapid fall or count below 100,000/µL is concerning in hypertensive disease and hemorrhage.
Clinical trapAn early hemoglobin can look reassuring during acute hemorrhage because plasma and red cells are lost together. Serial values and clinical perfusion are more informative than one number.
2. Hypertensive disorders and HELLP evaluation
| Test | Concerning pattern | Clinical meaning |
|---|---|---|
| Platelets | Falling trend; below 100,000/µL | Severe feature, consumption, bleeding and neuraxial implications |
| Creatinine | Above expected pregnancy baseline; >1.1 mg/dL or doubled baseline | Renal involvement and altered medication clearance |
| AST/ALT | Elevation, especially about twice normal with symptoms | Hepatic involvement; consider HELLP and other liver disease |
| Urine protein | 24-hour ≥300 mg or spot P:C ≥0.3 | Supports proteinuria; absence does not exclude severe features |
| LDH, bilirubin, haptoglobin, smear | Pattern consistent with hemolysis | Supports HELLP or another hemolytic process |
Uric acid may reflect disease severity in some contexts but is not a stand-alone diagnostic test. The transport clinician should report the pattern: symptoms, blood pressure, platelets, renal function, liver tests, urine output, and fetal trajectory.
A patient has severe hypertension, platelets 86,000/µL, creatinine 1.3 mg/dL, and normal urine protein. Can severe preeclampsia still be present?
Yes. Severe features can establish high-risk disease even without proteinuria.
3. Coagulation and obstetric hemorrhage
PT/INR and aPTT
Helpful when factor depletion, anticoagulant effect, liver dysfunction, or disseminated intravascular coagulation is suspected. Normal results do not exclude early coagulopathy.
Fibrinogen
Normally elevated in pregnancy. A value near the nonpregnant normal range can be relatively low during active hemorrhage; falling values are concerning.
Viscoelastic testing
Where available, TEG or ROTEM may provide rapid functional information and support targeted blood-product therapy.
Blood-bank readiness
Confirm type, antibody screen, crossmatch status, products available, transport cooler requirements, and massive-transfusion pathway.
4. Glucose, ketones, electrolytes, and acid–base status
Pregnancy can develop diabetic ketoacidosis at lower glucose concentrations than many clinicians expect. Do not exclude DKA because the glucose is only moderately elevated. Normal pregnancy also lowers PaCO₂ through increased minute ventilation; a PaCO₂ near 40 mm Hg may represent relative hypoventilation.
Paramedic knowledge bridgeUse the same acid–base framework you already know, but compare PaCO₂ and creatinine with pregnancy-specific baselines.
5. Infection and sepsis diagnostics
- Obtain cultures from appropriate sites before antimicrobials when this does not substantially delay treatment.
- Obtain and trend serum lactate in suspected maternal sepsis.
- Assess CBC, renal and liver function, coagulation, glucose, blood gas, and source-specific tests.
- Remember that maternal sepsis can occur without fever.
- Use laboratory data to identify organ dysfunction; do not rely on one screening score or one biomarker.
6. Blood type, antibodies, and transfusion testing
ABO and Rh
Confirm current type and whether the patient is Rh-negative.
Antibody screen
Identify clinically significant red-cell antibodies that affect crossmatching and fetal anemia risk.
Type and screen
ABO/Rh plus antibody screen; useful for patients who may need blood.
Crossmatch
Tests compatibility with selected donor units and supports rapid issue.
7. Trauma and fetomaternal hemorrhage
The Kleihauer-Betke test estimates fetal red cells in maternal circulation and can help quantify fetomaternal hemorrhage and guide Rh immune globulin dosing. It has sensitivity and interpretation limitations and must not replace fetal monitoring, obstetric evaluation, or clinical judgment. A negative test does not exclude placental abruption or all fetal-maternal bleeding.
8. Group B Streptococcus and microbiology records
CDC recommends GBS screening during the 36th or 37th week of each pregnancy. During transport, verify the current pregnancy result, allergy history, intrapartum antibiotics already given, dose times, rupture duration, gestational age, and maternal temperature. GBS status is one part of neonatal-risk assessment, not a substitute for evaluating chorioamnionitis or sepsis.
9. Point-of-care ultrasound
Focused obstetric
Fetal cardiac activity, presentation, gross fluid assessment, placental location, and selected biometry when trained.
Maternal cardiac
Gross ventricular function, pericardial effusion, right-heart strain pattern, and volume-response clues.
Maternal lung
B-lines, pleural sliding, effusion, and focal consolidation patterns.
Trauma/shock
Free fluid and focused causes of hypotension, while recognizing pregnancy-related anatomy and test limits.
Diagnostic limitationUltrasound cannot reliably exclude placental abruption, pulmonary embolism, or all causes of maternal shock. A technically limited or negative scan must not override a concerning clinical trajectory.
10. ECG and diagnostic imaging
Use ECG for chest pain, syncope, dysrhythmia, severe electrolyte disturbance, medication toxicity, or cardiopulmonary symptoms. Clinically necessary radiography, CT, MRI, or contrast-enhanced studies should not be withheld solely because the patient is pregnant when maternal benefit outweighs risk. Stabilize first, use the most appropriate test, and communicate gestational age and clinical urgency.
11. Preanalytic and transport errors
Record collection time and whether it was before or after fluids, medication, seizure, hemorrhage, or delivery.
Identify arterial, venous, line draw, urine, swab, or point-of-care source.
Consider hemolysis, dilution from IV fluids, clotting, mislabeling, and transport delay.
Compare with prior results rather than reading one value in isolation.
Report what changed and how it alters treatment, urgency, or destination.
12. Evolving case study
Phase 1: Sending results
The patient has severe-range hypertension, RUQ pain, platelets 118,000/µL, creatinine 0.9 mg/dL, and AST mildly elevated. The crew records collection times and requests the prior trend.
Phase 2: Trend changes
Repeat results show platelets 92,000/µL, creatinine 1.2 mg/dL, and AST more than twice normal. Urine output has fallen. The pattern is more important than any one value.
Phase 3: Transport implications
The team confirms magnesium and antihypertensive therapy, reviews blood-bank readiness, increases reassessment frequency, and sends the updated results to the receiving center.
Phase 4: Destination decision
Worsening fetal status and multisystem maternal laboratory deterioration prompt immediate discussion of the nearest facility capable of emergency delivery, anesthesia, blood-bank support, and neonatal stabilization.
13. High-yield chapter summary
- Pregnancy changes normal laboratory baselines.
- Trends and clinical context matter more than isolated values.
- Acute hemorrhage may precede a fall in hemoglobin.
- Platelets below 100,000/µL are a severe feature in hypertensive disease.
- Creatinine should usually be lower in pregnancy; a normal-high value may be abnormal.
- Proteinuria is not required when severe features are present.
- Fibrinogen is normally elevated; low-normal can be concerning in hemorrhage.
- DKA can occur with only moderate hyperglycemia.
- A PaCO₂ of 40 mm Hg can represent relative hypoventilation.
- Obtain lactate and appropriate cultures in suspected sepsis without delaying treatment.
- Review both Rh type and antibody screen.
- POCUS answers focused questions and cannot rule out every emergency.
- Necessary maternal imaging should not be withheld solely because of pregnancy.
- Time-link results to interventions and changes.
References
- International Board of Specialty Certification. Maternal Fetal Transport Microcredential Candidate Handbook. Updated April 2026.
- American College of Obstetricians and Gynecologists. Gestational Hypertension and Preeclampsia. Practice Bulletin No. 222.
- Society for Maternal-Fetal Medicine. Consult Series #67: Maternal Sepsis.
- Centers for Disease Control and Prevention. Screening for Group B Streptococcus Bacteria. 2025.
- Easter SR, et al. Point-of-care maternal ultrasound in obstetrics. American Journal of Obstetrics and Gynecology. 2023.
- American College of Obstetricians and Gynecologists. Guidelines for Diagnostic Imaging During Pregnancy and Lactation.
- Cheung KL, Lafayette RA. Renal physiology of pregnancy. Advances in Chronic Kidney Disease. 2013.
- Matsunaga S, et al. Fibrinogen for the management of critical obstetric hemorrhage. 2019.
Chapter assessment
Twenty-question laboratory and diagnostic assessment quiz
Immediate rationales are shown in study mode, and your score is stored locally.