Apolipoprotein A-1 (ApoA-I) — Serum
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mg/dL | 119 – 240 | 111 – 150 | 142 – 253 | 145 – 262 |
Apolipoprotein A-1 (ApoA-I) is the primary structural and functional protein of HDL and participates in reverse cholesterol transport and HDL-mediated antioxidant and anti-inflammatory effects.
Normal pregnancy increases ApoA-I, especially in the 2nd and 3rd trimesters, reflecting physiologic hyperlipidemia.
Normal physiology and pregnancy changes
Normal pregnancy
- Estrogen increases hepatic synthesis of ApoA-I and HDL.
- Gestational insulin resistance increases triglycerides and modifies HDL metabolism.
- ApoA-I typically rises progressively across pregnancy.
Laboratory considerations
- Reference intervals vary with assay method—use pregnancy-specific ranges when available.
- Interpret ApoA-I along with HDL-C, triglycerides, and metabolic indicators.
Causes of Low Apolipoprotein A-1
Pregnancy-related
- Preeclampsia and hypertensive disorders
- Gestational diabetes / insulin resistance
- Obesity or metabolic syndrome in pregnancy
- Severe hypertriglyceridemia
Cardiometabolic conditions
- Metabolic syndrome
- Type 2 diabetes; poorly controlled type 1 diabetes
- Nephrotic syndrome
Chronic/systemic illness
- Chronic inflammatory diseases
- Chronic liver disease
- Malnutrition, cachexia
- Acute severe inflammation or sepsis
Genetic causes
- Familial ApoA-I deficiency (rare)
- Tangier disease (ABCA1 deficiency)
- LCAT deficiency
Persistently low ApoA-I warrants evaluation of liver, renal, metabolic, and inflammatory status.
Causes of High Apolipoprotein A-1
Physiologic
- Normal pregnancy
- Constitutionally high HDL/ApoA-I phenotypes
- Benign CETP polymorphisms with elevated HDL-C
Medication effects
- Estrogen therapy (outside pregnancy)
- Niacin or investigational CETP inhibitors
Isolated high ApoA-I in pregnancy is usually not pathologic when liver function, triglycerides, and other lipid parameters are normal.
When to repeat or investigate further
- Markedly low ApoA-I with low HDL-C and early cardiovascular disease history
- Unexpectedly low levels in preeclampsia or metabolic disease
- Discordance between ApoA-I and HDL-C
- Unexplained deviation from baseline or early-pregnancy values
Interpret results alongside clinical history and full lipid profile.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table. Obstet Gynecol. 2009;114:1326-31.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed.
- Fischbach FT, Dunning MB. Manual of Laboratory and Diagnostic Tests. 7th ed.