Table 3:
Renal changes during normal pregnancy.
| Variable | Direction and magnitude of change in pregnancy |
|---|---|
| Renal, calyceal, and ureter size | Increases in bipolar diameter (1.0–2.5 cm); kidney volume increases by 25–30% |
| pH | Increases by about 0.02–0.06 |
| Renal blood flow | Increases by 60–80% |
| Glomerular filtration rate | Increases by 40–50% |
| Renal osmolality | Decreases by approximately 10 mOsm/kg of water |
| Urine protein excretion | Increases (up to 300 mg/day) |
| Serum creatinine | Decreases by 16, 23 and 20% in first, second & third trimester (normal pregnancy range: 0.4–0.6 mg/dL) |
| Blood urea nitrogen levels | Decreases to 8–10 mg/dL |
| Serum bicarbonate | Decreases (by 4–5 mEq/L) due to compensatory respiratory alkalosis |
| Renal albumin excretion | Increases |
| Renal AAG-1 excretion | Increases |
| Electrolytes | |
| Potassium (K) | Unchanged to mild decreases |
| Sodium (Na) | Decreases to approximately 130–135 mmol/L |
| Bicarbonate (HcO3) | Decreases by (18–22 mmol/L is normal range in pregnancy) |
| Chloride (Cl) | Unchanged |
| Phosphorus | Unchanged |
| Magnesium | Unchanged |
| Uric acid (serum) | Decreases by approximately 130–135 mEq/L |
| Aldosterone | Increases |
| Renin–angiotensin | Increases |
| Renal transporters | |
| BRCP | Slight increase in BRCP [20, 118] |
| MRP1 | Unchanged [81] |
| MRP2 | Decreased to unchanged expression of MRP2 in pregnant rats [81, 119] |
| MRP3 | Increased MRP3 (31–225%) [81, 118] |
| MRP4 | Decreased MRP4 [81, 89] |
| MRP5 | Decreased MRP5 [81] |
| MRP6 | Unchanged [81] |
| MATE1 | Decreased expression (by 20–40%) of MATE1 [118] |
| MATE2-K | Increased expression of MATE2-K |
| MDR1 | Unchanged to slight decrease MDR1 expression [20, 118] |
| OAT1 | Decreased expression of OAT1 [118] |
| OAT2 | Increased OAT2 expression [118] |
| OAT3 | Decreased expression of OAT3 [118] |
| OAT5 | Decreased OAT5 [118] |
| OAT1A6 | Decreased expression [118] |
| OAT2B1 | Increased expression [118] |
| OAT3A1 | Decreased OAT3A1 [118] |
| OATP4C1 | Increased during pregnancy |
| OCT1 | Increased OCT1 expression [118] |
| OCT2 | Increased OCT2 expression [118] |
| OCT3 | Decreased OCT3 expression [118] |
| OCTN1 | Decreased OCTN1 [118] |
| OCTN2 | Decreased OCTN 2 [118 ] |
| P-gp | No change in renal P-gp expression during pregnancy [120] |
| PEPT1 | Increased PEPT1 expression [118] |
| PEPT2 | Decreased PEPT2 expression [118] |
| URAT1 | Decreased expression of URAT1 [121] |
BRCP, breast cancer resistance protein; MATE, multidrug and toxin extrusion transporter; MDR, multidrug resistance protein; MRP, multidrug resistance-associated protein; OAT, organic anionic transporter; OATP, organic anionic transporting protein; OCT, organic cationic transporter; OCTN, organic cation/carnitine transporter; PEPT, peptide transporter; Pgp, P glycoprotein; URAT, urate transporter.