Kidney stones are common in pregnancy. Estimated prevalence ranges from 1 out of every 200-1,500 pregnancies. (1) The more pregnancies a woman has, the higher her risk of having kidney stones. Kidney stone risk increases from 5% to 12% in women with 3 or more pregnancies. (2)
Kidney stones are most likely to happen later in pregnancy. Up to 90% of kidney stones occur during the second or third trimester. (3) One study found that the risk of kidney stones doubled in the second trimester and increased further in the third trimester. (4)
So, why is there this association between kidney stones and pregnancy? And what can we do about it?
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Kidney Stones and Pregnancy: Why?
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The most likely reason that kidney stones are associated with pregnancy is that pregnancy increases the amount of kidney stone producing molecules in urine. Pregnant women have more blood to support the fetus, which increases the flow of blood to the mother’s kidneys. All this extra blood must be filtered, which results in more minerals and waste in the urine. (5)
As a result, pregnant women have higher amounts of substances like calcium, oxalate, and uric acid in their urine. All of these molecules can bind and form kidney stones. (1)
Although pregnancy also usually increases kidney stone inhibitors like citrate and magnesium, this increase is not proportional to the increase in kidney stone promoting molecules. (6)
Higher Urine pH
Pregnancy causes urine pH to go up, making urine less acidic. Kidney stones are more likely to form when urine pH is too high (or too low). Specifically, calcium phosphate stones are more likely to form with pH is too high. (7)
Indeed, calcium phosphate stones are most common during pregnancy. (1) This is very different than in the general population, where calcium oxalate stones are most common and calcium phosphate stones only make up about 12% of stones. (7)
Pregnancy causes changes to women’s anatomy that makes it difficult to empty the bladder completely. Any of you moms out there who remember running to the bathroom constantly know this well! In fact, a condition called hydronephrosis occurs in 90% of pregnant women. (1)
Because urine hangs out in the bladder for a longer time than usual, all of that extra calcium, oxalate and other molecules have more time to bind and form kidney stones. Stagnant urine can also increase the chance of infection.
Kidney Stone Symptoms in Pregnancy
The symptoms of kidney stones during pregnancy are similar to symptoms in people who are not pregnant.
The most common symptoms of kidney stones are: (8)
- Pain in the lower back that may radiate to your side, lower belly and groin
- Bloody urine
- Cloudy or smelly urine
- Painful urination
- Nausea & vomiting
- Fever and chills (if a kidney stone gets infected)
Kidney Stone Pregnancy Complications
Unfortunately, kidney stones during pregnancy can cause more than pain. Some of the more common complications of kidney stones in pregnancy include early delivery and preeclampsia.
- Early delivery
- C-section delivery
- Low birth weight
- Gestational diabetes
- Membrane rupture
How To Prevent Kidney Stones During Pregnancy
Drink Plenty of Water!
As always, the most important thing you can do to prevent kidney stones during pregnancy is to make sure to drink plenty of water. This will help dilute your urine, making kidney stones less likely.
Most people should aim for around 3 liters of fluid each day for stone prevention. (12) Ask your doctor how much water is right for you!
Of note, as much as you can, try not to hold your urine for long periods of time. Use the bathroom often. Keeping urine in your bladder for a long time gives kidney stones more time to form.
Control Your Blood Pressure
Blood pressure, preeclampsia and kidney stones in pregnancy are all related. (13) (14) Doing everything you can to control your blood pressure can help reduce the risk of kidney stones and complications during pregnancy.
Tips to control blood pressure:
- Eat plenty of fruits & veggies. The Dietary Approaches to Stop Hypertension (DASH) diet can lower blood pressure by 10 points!
- Watch the salt. Limit sodium to 1,500-2,300mg per day.
- Move your body! Daily physical activity is amazing for blood pressure control.
- Take time for self care. Stress alone can increase blood pressure and make it harder to manage.
- Cut out alcohol and cigarettes. Blood pressure control is yet another reason to avoid drinking and smoking during pregnancy!
You might want to take your blood pressure at home. Check out these tips for taking your own blood pressure.
Eat a Healthy Diet
Nutrition can play a big role in preventing kidney stones during pregnancy. Eating a healthy diet can help reduce the amount of calcium, oxalate and uric acid in your urine. Healthy eating can also increase good things in your urine that can prevent kidney stone formation, such as citrate.
Here are some general tips for healthy eating to prevent kidney stones during pregnancy:
- Keep sodium to 1,500-2,300mg per day.
- Make sure to get enough calcium! Aim for 3 servings of dairy or dairy substitute per day. As a bonus, calcium may help prevent preeclampsia. (15)
- Eat plenty of fruits and veggies! At least 5 servings per day is a good rule of thumb.
- Limit red and processed meats. These tend to increase uric acid levels.
Ask your dietitian for more specific information about healthy eating during pregnancy.
Stay On Top of Doctor Appointments
Lastly, the importance of going to all of your doctor’s appointments cannot be understated. Get all lab work and take any medications prescribed by your doctor as recommended.
Also, don’t be afraid to tell your doctor anything you notice about your body. More information is always better. Your doctors are there to help you!
Kidney Stone Treatment During Pregnancy
Finding & Assessing Kidney Stones During Pregnancy
The first step for kidney stone treatment is to get a picture of your kidney stone. Your doctor needs to know the size and location of your kidney stone to know how to treat it.
Usually, computerized tomography (CT scans) are used to get a good picture of kidney stones. However, CT scans use radiation, which can hurt the fetus. Instead, ultrasounds are usually used in pregnancy to get a picture of your kidney stone. Ultrasounds are much safer for the fetus.
Getting Rid of Kidney Stones During Pregnancy
After your doctor has a picture of your kidney stone, they will come up with a plan. In many cases, kidney stones can pass without medical intervention. Kidney stones less than 1 centimeter can usually pass without treatment. (1) Your doctor will probably recommend medication for pain and plenty of water to help the kidney stone pass.
In some cases, your doctor may have to remove the kidney stone. If the stone is large, in a bad location, or if it causes complications, your doctor is more likely to recommend removing the kidney stone.
Dangerous complications of kidney stones: (1)
- Uncontrolled pain
- Kidney function problems
- Persistent nausea or vomiting
Nephrostomy tubes are the most common way to get rid of kidney stones during pregnancy. Ureteroscopy may also be used. These treatments have become an option in the past few decades due to advances in kidney stone and pregnancy care. (1)
Of course, kidney stones are notorious for causing pain. Some of your “go-to” ways to manage kidney stone pain may not be safe during pregnancy.
Ask your doctor about safe ways to manage pain.
Can You Get Kidney Stones After Pregnancy?
The changes to your anatomy and urine chemistry that happen during pregnancy usually go back to normal post-partum. One study found that urine calcium, pH and supersaturation of calcium oxalate went back to normal postpartum. (16)
Of course, it is not impossible to get a kidney stone after pregnancy. About 10% of people in the United States will get a kidney stone at some point in their life, regardless of being pregnant. (7) But, the increased risk of kidney stones related to pregnancy appears to go away after giving birth. (16)
Planning for Pregnancy with Kidney Stones
What should you do if you have kidney stones and want to become pregnant? Know that most people with kidney stones have a healthy pregnancy. Having kidney stones doesn’t mean you should not have a baby!
However, there is a higher risk of complications during pregnancy for people with kidney stones. This discussion is worth a trip to your urologist. Tell your kidney stone doctor you are planning on becoming pregnant. If you have active kidney stones, your doctor might recommend removing them before becoming pregnant.
Make sure to tell your prenatal doctor that you have (or have had!) kidney stones. They might want to monitor you more closely.