Lab values
Pregnancy Lab Values
Pregnancy dilutes hemoglobin and raises WBC and fibrinogen; questions give their own cutoffs when they differ.
| Test | US units | SI units | Notes |
|---|---|---|---|
| Hemoglobin in pregnancy | 11 g/dL or higher (1st and 3rd trimester), 10.5 or higher (2nd) | 110 g/L or higher (1st and 3rd trimester), 105 or higher (2nd) | Lower is anemia (CDC). Dilution alone drops hemoglobin from about 13.3 to 12.1 SI: Lower is anemia (CDC). Dilution alone drops hemoglobin from about 133 to 121 g/L |
| Hematocrit in pregnancy | 33% or higher (1st and 3rd trimester), 32% or higher (2nd) | 0.33 L/L or higher (1st and 3rd trimester), 0.32 or higher (2nd) | Lower is anemia (CDC) |
| WBC in pregnancy | 5,700–15,000/mm³ (8–40 weeks) | 5.7–15.0 × 10⁹/L (8–40 weeks) | About the same through pregnancy (Dockree 2021). Up to 20,000–30,000 in labor and the first days after birth; back to normal within about 1 week SI: About the same through pregnancy (Dockree 2021). Up to 20–30 × 10⁹/L in labor and the first days after birth; back to normal within about 1 week |
| Platelets in pregnancy | 150,000/mm³ or higher | 150 × 10⁹/L or higher | Gestational thrombocytopenia: usually above 75,000, no bleeding, normal 1–2 months after birth. Below 100,000 with new hypertension meets preeclampsia criteria; below 50,000 is almost certainly ITP. Epidural usually needs 70,000 (ACOG) SI: Gestational thrombocytopenia: usually above 75 × 10⁹/L, no bleeding, normal 1–2 months after birth. Below 100 with new hypertension meets preeclampsia criteria; below 50 is almost certainly ITP. Epidural usually needs 70 × 10⁹/L (ACOG) |
| Fibrinogen in pregnancy | 300–590 mg/dL (3rd trimester) | 3.0–5.9 g/L (3rd trimester) | Most are above the nonpregnant upper limit of 400 (Sun 2021). In postpartum hemorrhage, 200 mg/dL or less predicts severe bleeding (Charbit 2007) SI: Most are above the nonpregnant upper limit of 4 g/L (Sun 2021). In postpartum hemorrhage, 2 g/L or less predicts severe bleeding (Charbit 2007) |
| Glucose challenge, 1-hour 50 g | Below 130–140 mg/dL (cutoff set by the practice) | Below 7.2–7.8 mmol/L (cutoff set by the practice) | Screen at 24–28 weeks (ACOG); at or above the cutoff, do the 3-hour 100 g test |
| Glucose tolerance, 3-hour 100 g | Fasting below 95, 1 h below 180, 2 h below 155, 3 h below 140 mg/dL | Fasting below 5.3, 1 h below 10.0, 2 h below 8.6, 3 h below 7.8 mmol/L | Carpenter-Coustan; 2 or more values at or above = gestational diabetes. NDDG cutoffs: 105, 190, 165, 145 SI: Carpenter-Coustan; 2 or more values at or above = gestational diabetes. NDDG cutoffs: 5.8, 10.6, 9.2, 8.0 |
| Gestational hypertension | Systolic 140 or diastolic 90 mm Hg or higher, twice 4 h apart, after 20 weeks | Systolic 140 or diastolic 90 mm Hg or higher, twice 4 h apart, after 20 weeks | Previously normal BP, no proteinuria or severe features; up to half go on to preeclampsia |
| Preeclampsia | Systolic 140 or diastolic 90 or higher after 20 weeks plus proteinuria or new organ signs | Systolic 140 or diastolic 90 or higher after 20 weeks plus proteinuria or new organ signs | Proteinuria: 300 mg/24 h or more, protein/creatinine ratio 0.3 or more, or dipstick 2+ only if nothing else is available SI: Proteinuria: 300 mg/24 h or more, protein/creatinine ratio 0.3 mg/mg (about 34 mg/mmol) or more, or dipstick 2+ only if nothing else is available |
| Severe features | Systolic 160 or diastolic 110 mm Hg or higher | Systolic 160 or diastolic 110 mm Hg or higher | Or platelets below 100,000, creatinine above 1.1 mg/dL or doubled, transaminases twice normal, pulmonary edema, new headache not relieved by medication, visual symptoms, severe RUQ or epigastric pain. Severe BP can be confirmed within minutes to treat promptly SI: Or platelets below 100 × 10⁹/L, creatinine above 97 µmol/L or doubled, transaminases twice normal, pulmonary edema, new headache not relieved by medication, visual symptoms, severe RUQ or epigastric pain. Severe BP can be confirmed within minutes to treat promptly |
| Fetal heart rate baseline | 110–160 beats/min | 110–160 beats/min | Mean over 10 min, rounded to 5 beats/min; below 110 for 10 min is bradycardia, above 160 tachycardia (NICHD) |
| Fundal height | Weeks of gestation ± 3 cm (20–38 weeks) | Weeks of gestation ± 3 cm (20–38 weeks) | At the symphysis at 12 weeks, halfway to the umbilicus at 16, at the umbilicus at 20. Off by 3 cm or more: growth ultrasound. After birth, halfway between symphysis and umbilicus by day 5–7 and no longer felt above the symphysis by 2 weeks |
| Postpartum hemorrhage | 1,000 mL or more, or any loss with hypovolemia signs, within 24 h | 1,000 mL or more, or any loss with hypovolemia signs, within 24 h | Any route of birth (ACOG). Tachycardia may be the earliest sign; soaking 1 or more pads in an hour is an urgent warning sign (CDC) |
Study the labs
- ABG Interpretation in 6 StepspH, PaCO₂, HCO₃⁻, compensation, anion gap and oxygenation, with worked examples
- Electrolyte ImbalancesNa, K, Ca, Mg and phos: normals, ECG clues, safe replacement, hyperkalemia steps
- Pediatric Assessment and EmergenciesPAT, vital signs, airway infections, febrile seizures, dehydration, arrest, choking and abuse
Other lab values
- Chemistry
- Hematology
- Coagulation
- Arterial blood gas
- Liver and pancreas
- Cardiac
- Therapeutic drug levels
- Urine
- Newborn
- Pediatric vital signs by age
- Pediatric labs that differ from adults
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Sources
- ACOG PB 222 (2020) and 207 (2019); CDC MMWR 1998; Merck Manual (ACOG PB 190; physiology of pregnancy, prenatal evaluation, postpartum care); MedlinePlus 2026; Dockree 2021 (WBC); Sun 2021 (fibrinogen); StatPearls 2025 and AAFP 1998 (fundal height); CDC Hear Her 2024; AAFP 2017 (ACOG PPH definition); NICHD 2008 via AAFP 2020
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow your local protocols and medical direction.