Renal Complications in Normal Pregnancy - An Overview

Introduction:

The physiological, as well as anatomical changes in the woman's body start to appear during the early stages of the first trimester of pregnancy. A good understanding of the normal changes during pregnancy is important to diagnose the condition as well as to manage it efficiently. Renal complications occurring in normal pregnancy would range from mild urinary tract infections to serious illnesses such as renal failure. Hence, proper care and continuous monitoring are essential to improve the outcome.

Physiological Changes of Pregnancy:

Various physiological changes occurring during pregnancy include:

Hemodynamic Changes:

• Increased cardiac output.

• Decreased systemic blood pressure.

• Decreased vascular resistance.

• Increased nitric oxide levels in the blood.

• Increased levels of relaxin in the blood.

• Increased progesterone levels.

Volume Changes:

• Increased plasma volume of 40 to 50%.

• Increased total body water content.

• Decreased plasma osmolality by 10 mOsm/kg.

• Decreased plasma albumin.

Changes in Acid-Base Balance:

• Increased blood pH from 7.42 to 7.44.

• Mild respiratory alkalosis.

• Increased bicarbonate reabsorption.

• Decreased serum hydrogen ion.

• Decreased PCO2 (18 to 22 mEq/L).

Hormonal Changes:

• The decreased osmotic threshold for thirst.

• Increased metabolic clearance.

• Increased levels of vasopressin, aldosterone, mineralocorticoids, etc.

• Increased renal kallikrein excretion.

Physiological and Anatomical Renal Changes that Occur in Pregnancy:

• Increased renal size and volume.

• Dilatation of the collecting duct.

• Ureteral connective tissue hyperplasia.

• Ureteral smooth muscle hypertrophy.

• Physiologic hydronephrosis can happen due to the enlarging uterus putting pressure on the kidneys.

• Urine retention also happens due to hydronephrosis.

• Increased urinary protein excretion (proteinuria) to a range of 180 to 250 mg/day.

• A 50% increase in the glomerular filtration rate happens in the second trimester. This results in hyperfiltration, thereby reducing the serum creatinine levels to a range of 0.4 to 0.6 mg/dl.

• A 50 to 80% increase in renal blood flow.

• Decrease in renal vascular resistance.

• Hyperfiltration of sugar, amino acids, vitamins, proteins, etc.

• Positive sodium balance.

What Are the Renal Complications in Normal Pregnancy?

The renal complications that can occur during the stages of normal pregnancy are as follows:

• Acute kidney injury.

• Lupus nephritis.

• Atypical hemolytic uremic syndrome.

• IgA nephropathy.

• Diabetic nephropathy.

• Nephrotic syndrome in pregnancy.

• Chronic kidney disease in pregnancy.

• End-stage renal disease in pregnancy.

What Are the Complications of Acute Kidney Injury in Normal Pregnancy?

Previously, acute injury to the kidney as a consequence of pregnancy was one of the main causes of maternal and fetal death worldwide. In recent times, the incidence has been decreasing as a result of improvements in prenatal care.

• Causes:

  • Sepsis from septic abortions.

  • Hemorrhage.

  • Preeclampsia (pressure during pregnancy).

  • Thrombotic microangiopathy.

  • Acute fatty liver.

  • Postpartum hemorrhage.

• Diagnosis: The diagnosis of acute kidney injury is difficult due to the vast number of physiological and hormonal changes that mask a renal injury. Few studies report an increase in serum creatinine levels to a value of 0.3 mg/dl than the normal reference range.

What Are the Complications of Lupus Nephritis in Normal Pregnancy?

The occurrence of systemic lupus erythematosus (SLE) in the kidney is attributed to the immunological changes that occur at the time of conception.

• Causes:

  • It can be associated with the immunological changes that occur at the time of conception.

  • Studies report that the patients with renal symptoms demonstrated anti-DNA antibodies and low C3 levels. Patients who developed lupus nephritis in the second and trimester of pregnancy demonstrated low C4 levels and high anti-C1 q antibodies.

• Diagnosis: Diagnosis of this condition is established by the detection of antinuclear antibodies in the patient's serum.

• Complications:

  • High risk of preterm delivery.

  • High chances of developing preeclampsia.

  • The estimated overall mortality rate is one percent.

• Treatment: Safer drugs should be prescribed to prevent any adverse effects; drugs such as Hydroxychloroquine and Azathioprine can be used to suppress the autoantibodies.

What Are the Complications of Atypical Hemolytic Uremic Syndrome in Normal Pregnancy?

The atypical hemolytic uremic syndrome is a condition that is characterized by decreased kidney function, microangiopathic hemolytic anemia, and thrombocytopenia.

• Causes: Studies suggest that atypical hemolytic uremic syndrome may be caused by any factor or process that activates the alternative complement pathway. Pregnancy is believed to be one such factor that triggers the activation of alternative complement pathways, thereby developing the atypical hemolytic uremic syndrome.

• Complications:

  • Death of a fetus in the womb.

  • Preeclampsia.

  • Progress to end-stage renal disease in around 76% of cases.

• Diagnosis: Diagnosis of this condition is a bit difficult as many conditions show similar features. Hence, treatment should be initiated at the earliest as the symptoms are noticed.

• Treatment: Plasma exchange should be initiated in these patients, and drugs such as Eculizumab can be prescribed to control the disease.

What Are the Complications of IgA Nephropathy in Normal Pregnancy?

IgA nephropathy is characterized by the deposition of IgA antibodies in the kidney, affecting normal kidney function.

• Causes: The main reason behind pregnant women developing IgA nephropathy is age, as this condition is more common in the second and third decades of life, and it affects women of childbearing age.

• Complications:

  • Preterm delivery.

  • Pregnancy loss.

  • Preeclampsia.

  • Low birth weight babies.

• Treatment: Patients with mild IgA nephropathy usually do not require any treatment. In patients with severe disease conditions, safer immunosuppressive agents should be prescribed.

What Are the Complications of Diabetic Nephropathy in Normal Pregnancy?

Diabetic nephropathy is one of the common complications of type I and type II diabetes. It is caused as a result of poorly controlled diabetes which can cause damage to blood vessels in the kidneys. Studies report that six percent of pregnant women present with type 1 diabetes, and type 2 diabetes-associated nephropathy is less common.

• Complications:

  • Decreased renal function.

  • Progress to end-stage renal disease.

  • Proteinuria - increased urinary excretion of protein.

  • Preeclampsia.

  • Miscarriage.

  • Congenital malformations.

  • Macrosomia.

  • Preterm delivery.

  • Perinatal mortality.

• Treatment:

  • Oral hypoglycemics such as Glyburide and Metformin can be given in patients with type 2 diabetes mellitus.

  • Insulin therapy is recommended in patients with both types of diabetes.

What Are the Complications of Nephrotic Syndrome in Normal Pregnancy?

Nephrotic syndrome is characterized by the passage of excessive amounts of protein in the urine. In pregnant women, nephrotic syndrome can be caused due to many reasons resulting in heavy proteinuria.

• Causes:

  • Preeclampsia.

  • Minimal change disease.

  • Focal segmental glomerulosclerosis.

  • Membranous nephropathy, etc.

• Complications :

  • Heavy proteinuria (excessive loss of protein in the urine).

  • Systemic vasoconstriction results in placental hypoperfusion.

  • Decreased kidney function.

What Are the Complications of Chronic Kidney Disease in Normal Pregnancy?

Chronic kidney disease is characterized by the improper functioning of the kidneys, which lasts for a longer period of time. Women with an antepartum renal disease with serum creatinine levels of more than 2 mg/dl are at a higher risk of renal failure.

• Causes: It may occur as a result of pre-existing diseases such as diabetes, lupus nephritis, hypertension, etc.

• Complications:

  • Decreased renal function.

  • Preeclampsia.

  • Preterm delivery.

  • HELLP syndrome (a serious complication of pregnancy that mainly affects the blood and the liver).

  • Stillbirths.

  • Miscarriages.

  • Neonatal death.

  • Low birth weight.

• Treatment:

The main aim of treatment is to treat the underlying disease to prevent the further progression of renal disease. The patient should be informed priorly to the complications of pregnancy with the pre-existing renal disease. Careful monitoring and neonatal care would help improve the survival rates.

What Are the Complications of End-Stage Renal Disease (ESRD) in Normal Pregnancy?

Pregnant women with ESRD require dialysis. Studies report that patients under dialysis have diminished fertility rates due to irregular or absent menstrual periods. However, during the first year of dialysis, the chances of women getting pregnant are comparatively high.

• Causes:

ESRD in pregnant women is a rare complication, but if it occurs, it can be caused due to underlying systemic diseases such as poorly controlled diabetes, hypertension, lupus nephritis, autoimmune conditions, etc.

• Complications:

  • High mortality rates.

  • Fetal death.

  • Stillbirth babies.

  • Preterm delivery.

• Treatment:

Intensive dialysis is the mainstay of treatment in pregnant women with end-stage renal disease.

Conclusion:

Renal complications in pregnancy can range from mild urinary tract infection to end-stage renal disease requiring intensive dialysis. Thus, both the patient as well as the physician should understand the physiologic changes, renal diseases, and their outcomes in pregnancy. Marked improvement in the maternal and fetal outcomes in pregnancies complicated with renal diseases has occurred with good obstetric care and earlier interventions.