During which pregnancy stage is glomerular filtration rate increased?

Increased glomerular filtration rate (GFR) occurs predominantly during the second trimester of pregnancy. During this stage, significant physiological adaptations take place as the body adjusts to the demands of supporting the developing fetus.

The increase in GFR is primarily due to the rise in blood volume and renal blood flow that occurs as a result of hormonal changes, including increased levels of progesterone and relaxin. These hormones promote vasodilation, leading to enhanced renal perfusion and, consequently, an increased GFR. This adaptation is vital as it allows for more efficient clearance of waste products and the maintenance of fluid and electrolyte balance, which is crucial for both maternal and fetal health.

In contrast, during the first trimester, while there are some initial increases in blood volume and hemodynamic changes, the significant increase in GFR is not yet fully realized. By the third trimester, although GFR might still be elevated, it may plateau or even slightly decrease as the growing uterus exerts pressure on pelvic blood vessels, potentially reducing renal perfusion compared to the peak seen in the second trimester. Postpartum, GFR typically returns to pre-pregnancy levels as the body readjusts.

Understanding these physiological changes is important for nurses and healthcare providers when