Pregnancy causes and necessitates significant changes in the structure and function of the kidney. This causes kidney growth, increased blood flow, and above-average kidney function throughout the pregnancy. Understanding the normal physiological function of the kidneys during pregnancy will also help in understanding when there is a deviation and the kidney function has become abnormal. Read on to know more about the changes your kidney might undergo during pregnancy.
Normal Renal Changes during PregnancyDuring normal pregnancy, there are substantial functional, structural, and hemodynamic changes that take place in the body. Due to the vascular and interstitial space the kidney increases in size by 1 to 1.5 cm. Hydronephrosis is a physiological change at the time of pregnancy as a result of the mechanical obstruction of the ureters due to a growing fetus.
Research shows that the GFR (Glomerular Filtration Rate) keeps changing with each trimester. GFR increases by 20% and 45% at 4 and 9 weeks gestation, respectively. GFR was found to be 40% greater at term than in nonpregnant women, but later it came back to normal, nonpregnant levels 1 month following delivery.
As the pregnancy progresses, the link between RPF (Renal Plasma Flow) and GFR alters. Because RPF exceeds GFR in early pregnancy, the filtration fraction is slightly smaller than in nonpregnant controls. This changes between week 12 and the third trimester, when RPF returns to pre-pregnancy levels while GFR remains raised, resulting in an increased filtration percentage. All of these numbers return to normal after 4-6 weeks post-delivery.
Renal Dysfunctions Due to Pregnancy ComplicationsIn order to identify causes of decreased kidney function, it may be helpful to categorize them into prerenal, intrinsic renal, and postrenal factors. It is important to consider the causes involved in nonpregnant states. Certain causes, however, are either more common or unique to pregnancy.
Most of the time trying to correlate with pre-pregnancy data and symptomatology might help find the cause of Renal dysfunctions. In many cases, some renal dysfunctions such as CKD might go totally unrecognized up until pregnancy. However, there also exist complications that may arise due to complications during pregnancy like hyperemesis gravidarum, antenatal bleeding, etc.
1. Conditions with a fluid loss like hyperemesis gravidarum and antepartum hemorrhage can lead to prerenal dysfunction. Several factors including abruptio-placenta or septic abortion may cause acute renal cortical necrosis. Intrinsic renal disease specific to pregnancy is seen with pre-eclampsia and eclampsia.
2. Pre-eclampsia, eclampsia, HELLP (Hemolysis, Elevated Liver enzymes, Low Platelet), and acute fatty liver of pregnancy have very similar pathophysiology. Also, their presentations are very much similar to each other. It is important to carry out necessary investigations in order to arrive at a final diagnosis of these conditions.Recent studies have shown that preeclampsia occurs in around 3-5% of all pregnancies and leads to significant morbidity and mortality of the mother and the infant.
- Another common condition in pregnant women is Chronic Kidney Disease (CKD), which may be present early but in most cases is discussed only during pregnancy. In the case of CKD, the conception chances are low as there is reduced fertility and an increased risk of early miscarriages.
- CKD is classified into 5 stages during pregnancy. Stages 1 & 2 called normal or mild renal impairment with persistent albuminuria, affect around 3% of women of childbearing age. Stages 3-5 affect around 1 in every 150 women of childbearing age. The most common way to classify women with chronic kidney disease during pregnancy is based on serum creatinine levels, but we estimate that one in 750 pregnancies is complicated by stages 3-5 of CKD.
- Other thrombotic microangiopathies, while not as frequent as pre-eclampsia, cause significant morbidity and mortality during pregnancy and show diagnostic parallels to pre-eclampsia. Hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), and primary and secondary antiphospholipid syndromes are examples of diseases in this group.
Normal Renal Physiology during pregnancyThe kidney produces more erythropoietin, active vitamin D, and renin during a healthy pregnancy. Increased renal blood flow causes a more than 50% rise in glomerular filtration rate from early pregnancy.
Because gestational hyperfiltration is associated with a relative decrease in serum creatinine and urea concentrations, values deemed acceptable in the non-pregnant state may be problematic in pregnancy. On ultrasonography, the plethoric kidneys appear bigger, and when paired with the renal pelvis and ureteric dilatation, these normal pregnancy alterations mimic outflow blockage.
Effects of Pregnancy on an abnormal kidneyWomen with chronic kidney disease are less able to make the renal adaptations needed for a healthy pregnancy. Their inability to boost renal hormones often leads to normochromic normocytic anemia, reduced expansion of plasma volume, and vitamin D deficiency.6 The gestational rise in glomerular filtration rate is blunted in women with moderate renal impairment and usually absent in those with a serum creatinine higher than 200 µmol/l.4 7 8.
If preeclampsia develops, maternal renal function often deteriorates further, but the addition of a prerenal insult that will reduce renal blood flow, such as peripartum hemorrhage or regular use of a non-steroidal anti-inflammatory drug, can seriously threaten maternal renal function. In such circumstances, nephrotoxic drugs must be avoided and maternal circulation restored with careful fluid management, as women with pre-eclampsia are prone to pulmonary edema.
Normal pregnancy causes a number of coordinated changes in the kidney anatomy and hemodynamics. Our comprehension of these alterations is still limited, and additional research is needed in this area. Many illnesses can cause renal failure during pregnancy, posing risks to both mother and child. A better understanding of these illnesses, including their indicators and predictions, as well as better treatment alternatives, should improve our practice in the near future.
Role of a trained physician in reducing the renal disease burden in pregnancy
Early detection of the renal condition during or even in some cases before the pregnancy in the case of CKD will be helpful in reducing the overall risk of complications during pregnancy. In 30% to 60% of women with CKD, hyperprolactinemia occurs. Uremic toxins and a lack of anti-Müllerian hormone (AMH), compromise follicle quantity and can impair ovarian function and reduce the ovarian reserve. In such cases, timely treatment of renal conditions may restore fertility. In pregnancy conditions associated with raised creatinine levels, albuminuria and proteinuria need to be treated accordingly in order to reduce maternal and fetal morbidity and mortality rates.
Upskilling with relevant field-specific skills will help you to effectively screen and treat patients with renal conditions and reduce the burden of renal diseases associated with pregnancy.
A Fellowship in Nephrology course will aid you with all the necessary knowledge to understand the physiology of normal renal functioning as well as the pathophysiology of kidneys in various renal diseases and how to manage such cases efficiently.
The Fellowship in Nephrology course covers core competencies namely:
- Guidance in image interpretation, clinical consequences, and suggestions for tailoring interventions.
- Renal Replacement Therapy: What non-nephrologist should know.
- Special consideration among women, children, the elderly, pregnancy, and patients with concurrent disease states.
- Facilitate timely preparation for care of end-stage renal disease.
- Medication Safety in preventing nephrotoxicity.
Key Features of the Fellowship in Nephrology by Medvarsity include:
- Review and advance your knowledge of current practice and recent advances in nephrology
- Clinical case discussions for optimal clinical orientation
- Interactive features & self-assessment exercises to build your skill
- Explore evidence-based approaches and updated guidelines regarding kidney care
- 8-week Contact Program at leading Hospitals