The Kidney and Pregnancy


This is a particularly important topic because of the societal pressures and premium often given to having children, frequently at the risk of the life and health of the mother. This goal of this post is not to substitute for the professional services of the doctor/obstetrician who must be seen early and often during pregnancy but to empower patients during pregnancy so that they are aware of normal changes, possible issues that may arise involving the kidney, questions to ask their doctor and general best habits and practices to maintain kidney health during pregnancy.

Previously we have shared thoughts about pregnancy in dialysis and transplant patients. In this blog posts we will share our perspective on the issues that can arise and involve the kidney during pregnancy in patients with or without any known or prior kidney disease. To start the conversation, let’s talk about normal changes in the kidney and urinary tract during pregnancy before talking about what’s abnormal

The urinary bladder is pressed on by the uterus as it enlarges with the growing baby

In a normal pregnancy there are many changes in the kidneys and urinary tract that are not a sign of a problem but just a sign that the body is changing to accommodate the needs of the mother and growing baby

  • The increased blood volume and heart output during pregnancy causes about 50% increase in blood flow to the kidney. This causes an increased elimination of waste and reduced blood levels of urea, creatinine, urate and bicarbonate.
  • Mild amounts of glucose and/or protein in the urine may occur because the increase in blood supply to the kidney may exceed the ability of the kidney to reabsorb glucose and protein.
  • Pregnancy hormones increase the retention of salt and water by the kidney. This can cause leg swelling and reduction of concentration or plasma osmolality of the blood.
  • Pregnancy hormones also cause the smooth muscle of the urinary tract to become relaxed and dilated, kidneys increase in length and ureters become longer, more curved and with an increase in residual urine volume.
  • The increase in size of the womb or uterus presses on the bladder and reduces the space for the bladder to expand and store urine. So pregnant women often urinate often. Bladder smooth muscle however also relaxes, increasing capacity and risk of urinary tract infection
    2-10% of women have bacteria in the urinary tract during pregnancy and if untreated up to 30% may develop acute pyelonephritis- an infection of the kidneys which can be serious leading to problems like premature delivery and overwhelming infection of the mother

However, there are a number of changes that can arise involving the kidneys or urinary tract during pregnancy that are not normal. These problems include:

  1. Urinary tract infections. Sometimes there may be no symptoms to mild symptoms like frequent urination to more severe symptoms like fever, pain and bloodstream infection. At every visit and if you have any symptoms like those just mentioned, talk to your doctor, get tested for possible urine infection and get treated. There are several antibiotics that can be taken safely during pregnancy
  2. Blood in the urine (Also called Hematuria). 1 to 3 out of every 10 pregnant women will have hematuria at some point in pregnancy. 75% will resolve after delivery. Most common cause is vaginal bleed or urinary tract infection. Not always linked to increased risk of preeclampsia, hypertension or premature delivery. If you see blood in your urine, see your doctor, talk about what you see and how you feel. The doctor will likely get a urine test to make sure you don’t have a urine infection. The doctor may get an ultrasound of the kidneys and bladder to see of you have a kidney stone. Ultrasound scans are safe and pregnancy does not increase risk for kidney stones but if one is found, you likely had the stone before the pregnancy.
  3. Kidney disease during pregnancy. Kidney disease may preexist and be known, preexist and be discovered during pregnancy, or be new onset in pregnancy. Ability to sustain pregnancy depends on kidney function and blood pressure levels rather than the cause of kidney disease. Kidney function may decrease irreversibly during pregnancy and after delivery. Increased urinary protein excretion has worse outcome. Diabetes (high blood sugar), lupus, cystic kidney disease are all conditions that can worsen kidney function during pregnancy. Talk to your doctor about these so that a treatment plan can be developed to ensure you and your baby are safe.
  4. Hypertension in pregnancy. The kidney is an important organ in controlling blood pressure so it make sense that issues impacting the kidney can cause abnormal blood pressure in pregnancy. Hypertension affects 1 to 3 out of every 10 pregnancies. For hypertensive patients in pregnancy, most cases become hypertensive during pregnancy and this may continue after delivery. If you develop hypertension in pregnancy, you must be extremely careful, see your doctor and get the hypertension treated. There are several medications that can be used to treat high blood pressure in pregnancy safely. Hypertension can become a very serious condition called preeclampsia which can not only destroy the kidneys but lead to pregnancy loss, liver and even brain damage.

 

Questions

1. If I have kidney disease but I am not yet on dialysis, can I get pregnant? Yes it is possible. How easily you get pregnant depends on how severe your kidney disease is and the cause of your kidney disease. If you are a dialysis patient it is not impossible to get pregnant but it is a challenge and will require the skill of a kidney specialist that knows what to do working with your obstetrician

2. If I have kidney disease will it get worse if I try to get pregnant? It might get worse. You need to tell your doctor before you get pregnant if you already have kidney disease so the doctor can determine your risk of progressive or advanced kidney disease due to pregnancy. For some patients, the risk is too high and they may end up with kidney failure requiring dialysis or transplant after delivery. You may be advised not to become pregnant if your kidney disease is severe.

3. The doctor told me about doing a biopsy during the pregnancy to better understand why my kidney is having trouble. Should I do it? That decision is yours but ask to your doctor to describe the risks and benefits of the biopsy. If the benefit does not exceed the risk, you can decide to not do the biopsy or do it after the delivery.

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