From the Research
The normal range of urine osmolality during pregnancy is typically less than 500 milliosmoles per kilogram (mOsm/kg), as values above this threshold may indicate inadequate fluid intake and decreased hydration status, according to the most recent study 1.
Key Points
- Urine osmolality reflects the renal regulation of excess fluid or deficit fluid and serves as a marker of hydration status 2.
- Physiological changes in kidney function during pregnancy lead to increased glomerular filtration rate and altered tubular reabsorption, resulting in a tendency toward more dilute urine.
- The lower urine osmolality reflects the body's adaptation to pregnancy, which includes increased water retention to support the expanded blood volume needed for fetal development and placental function.
- Urine color can be used as a practical and valid marker of urine concentration in pregnant and lactating women, with a urine color of 4 or more indicating a urine osmolality of 500 mOsm/kg or higher 1.
Clinical Implications
- Pregnant women should aim to maintain a urine osmolality below 500 mOsm/kg to ensure adequate hydration status.
- Urine color can be used as a simple and non-invasive tool to monitor hydration status in pregnant and lactating women.
- Women who present with a urine color of 4 or more should consider increasing their fluid consumption to improve hydration status 1.