Creatinine (serum / plasma)
Creatinine normally decreases in pregnancy because of increased glomerular filtration rate (GFR). Even small increases may suggest renal impairment or preeclampsia.
| Units | Nonpregnant Female | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mg/dL | 0.5 – 0.9 | 0.4 – 0.7 | 0.4 – 0.8 | 0.4 – 0.9 |
| µmol/L | 44 – 80 | 35 – 62 | 35 – 71 | 35 – 80 |
Pregnancy physiology
- GFR increases 40–50% beginning early in pregnancy.
- Serum creatinine falls accordingly (commonly <0.6 mg/dL).
- A creatinine ≥1.0 mg/dL is usually abnormal in pregnancy.
- Hydration status can cause small fluctuations.
Causes of elevated creatinine in pregnancy
- Preeclampsia / severe features
- Acute kidney injury (AKI)
- Chronic kidney disease
- Dehydration
- Obstructive uropathy
- Renal lupus or autoimmune nephritis
- Medication-related renal dysfunction (NSAIDs, calcineurin inhibitors)
Creatinine >0.9 mg/dL in later pregnancy usually warrants evaluation; >1.1 mg/dL is part of diagnostic criteria for preeclampsia with severe features.
Causes of low creatinine
- Normal physiologic pregnancy increase in GFR
- Low muscle mass
- Overhydration / IV fluids
- Malnutrition or sarcopenia
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.