Estimated Glomerular Filtration Rate (eGFR)

During pregnancy, eGFR naturally increases due to physiological changes that support maternal and fetal health. ​In this article, we’ll cover the optimal eGFR ranges in pregnancy, explore causes of elevated or reduced values, and discuss how pregnancy-specific changes affect kidney filtration. 

eGFR Testing

The estimated glomerular filtration rate (eGFR) is a blood test that provides an estimate of the glomerular filtration rate (GFR), a key measure of kidney function. 

GFR is the rate at which the kidneys filter waste products and excess substances from the blood. The eGFR is used to assess how well the kidneys function and is an important tool for diagnosing and monitoring kidney diseases. GFR is typically estimated by measuring the concentration of creatinine in the blood. 

The most commonly used equation for estimating eGFR is the Modification of Diet in Renal Disease (MDRD) Study equation:

eGFR = 175 × (sCR/88.4)-1.154 × (Age)-0.203 × (0.742 for females) × (1.210 if Black)

This is an estimate and is not exact. 

The glomeruli are clusters of specialized capillaries in the renal cortex. Blood from the renal artery flows into these capillaries. The glomerular filtration barrier consists of three main layers: the endothelium (innermost layer), the basement membrane (middle layer), and the podocytes (outermost layer). Blood enters the glomerulus via the afferent arteriole, which is under high pressure due to the narrower exit of the efferent arteriole. This high pressure facilitates filtration. 
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As blood flows through the glomerular capillaries, the filtration barrier allows small molecules like water, electrolytes, and waste products (creatinine, urea) to pass through while retaining larger molecules such as proteins (like albumin). The filtered fluid, known as the filtrate, collects within Bowman’s capsule. This filtrate contains water, electrolytes, waste products, and other substances. The glomerular filtration barrier is highly selective and designed to allow the passage of essential substances while restricting the entry of larger molecules. This selectivity is crucial for maintaining the composition of the blood while eliminating waste products.

​eGFR in Pregnancy

Glomerular filtration increases by 40-50% during a normal pregnancy. The eGFR values are the highest value at approximately the 24th week. Subsequently, serum creatinine, BUN, electrolytes, proteins, and uric acid values decrease.

​eGFR is reported as a measure of kidney function in pregnancy, even though it is acknowledged that it consistently underestimates function.

High eGFR in Pregnancy

There is limited data on the application of this indice in pregnancy.

Most Common Causes of High eGFR in Pregnancy

• Decreased Serum Creatinine
• Advanced Maternal Age
• Hyperthyroidism
• Decreased Muscle Mass
• Anorexia

Low ​eGFR in Pregnancy

​In cases of preeclampsia, the GFR and renal plasma flow decrease by between 30% and 40% compared to normal pregnancy pregnancies of the same duration. 

​Preeclampsia may lead to kidney disease by causing acute kidney injury, endothelial damage, and podocyte loss, which affects GFR.

Most Common Causes of Low ​eGFR in Pregnancy

• Renal Inflammation/Damage
• Hypothyroidism
• Obstruction (Kidney Stones, Hydronephrosis)
• Oxidative Stress
• Low Progesterone
• Severe Dehydration
• High Cortisol
• Hyperhomocysteinemia
• Environmental Chemical Exposure
• Heavy Metal Exposure
• Nutritional Deficiencies (vitamin D, choline, vitamin B2 (riboflavin), vitamin B12 (cobalamin), vitamin B9 (folate), vitamin B6 (pyridoxine))

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Medical Disclaimer:
This content is for educational purposes only and is intended for licensed medical professionals. It is based on current research, subject to change, and not intended to diagnose, treat, or prevent any medical condition. This information does not replace consultation with a qualified healthcare provider. Seek professional medical evaluation and treatment from a licensed provider. Use of this information is at your own risk.

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