For most women who have experienced both, kidney stones are actually more painful than giving birth. In a study published in the Journal of Pain Research, 63% of women who had been through both labor and a kidney stone episode rated the kidney stone as worse. Another 16% said the pain was about equal, while only 21% found childbirth more painful. On the McGill Pain Index, which scores pain out of 50, kidney stones land around 42 while childbirth scores roughly 32.
So the common comparison isn’t just folk wisdom. For many people, passing a kidney stone ranks among the most intense pain the human body can produce.
Why Kidney Stones Hurt So Much
The pain isn’t really about a sharp rock scraping its way through your body, though that image is hard to shake. The main driver is pressure. When a stone blocks the ureter (the narrow tube connecting your kidney to your bladder), urine backs up behind it. That trapped urine stretches the kidney and the walls of the ureter, triggering an intense pain response.
Making things worse, your body responds to the blockage by releasing inflammatory compounds called prostaglandins. These do two unhelpful things at once: they cause the smooth muscle of the ureter to spasm around the stone, and they increase blood flow to the kidney, which produces even more urine and drives the pressure higher. It’s a feedback loop that escalates the pain rapidly.
Your ureters are only about 3 to 4 millimeters wide in most adults. A stone doesn’t need to be large to completely block that tiny channel. Research has found no correlation between stone size and pain severity, meaning a 2-millimeter stone can hurt just as much as a larger one if it lodges in the wrong spot. Location matters more than size.
If the backup of urine is severe enough, the kidney itself begins to swell, a condition called hydronephrosis. This can add nausea, vomiting, blood in the urine, and pain that radiates from your back around to your abdomen and groin. Because the kidney and the intestines share nerve pathways, the nausea can be relentless.
How Labor Pain Works Differently
Labor pain comes from a fundamentally different process. As the uterus contracts, its muscle fibers stretch and tighten to push the baby downward. That stretching floods the muscle cells with calcium and sodium ions, changing the electrical signals in the tissue and triggering powerful, rhythmic contractions. The cervix dilating adds another layer of pain as tissue that doesn’t normally stretch is forced open.
The key difference is the pattern. Labor pain builds in waves. Contractions intensify, peak, and then ease off, giving the body brief windows of relief between them. Kidney stone pain, by contrast, can hit suddenly at full intensity and stay there for minutes to hours without any letup. Many people describe it as a constant, crushing ache in the flank that comes on within minutes and doesn’t relent. That relentless quality is a big part of why kidney stone sufferers rate it so highly on pain scales.
Duration and Timing
Active labor for a first-time birth typically lasts several hours, sometimes longer, but the pain follows a trajectory. Early contractions are milder and widely spaced, growing more intense as delivery approaches. There’s a sense of progression, and in many cases, pain relief options like epidurals are available partway through.
A kidney stone episode can last anywhere from 20 minutes to several hours per attack, and attacks can recur over days or weeks as the stone works its way down the ureter. Some stones pass in a day. Others take weeks, with unpredictable flare-ups of severe pain that can strike at any time, including in the middle of the night or during a work meeting. That unpredictability adds a psychological burden that labor, with its more defined timeline, doesn’t carry in the same way.
Pain Relief Options
For labor, epidurals are highly effective and widely available in hospital settings. They can reduce contraction pain dramatically, which is one reason many women’s overall memory of labor pain is more manageable than the peak moments might suggest.
For kidney stones, the first-line approach is usually anti-inflammatory medications that target the prostaglandins driving the pressure and spasms. Stronger pain medications may be needed in the emergency room. If a stone won’t pass on its own, a procedure called ureterorenoscopy allows doctors to go in through the urinary tract and break up or remove the stone. Recovery from this tends to involve less pain than the stone itself, particularly when spinal or epidural anesthesia is used during the procedure.
Smaller stones (generally under 5 or 6 millimeters) often pass on their own with hydration and pain management over a few days. Larger stones or those causing complications like infection are more likely to need intervention.
Why the Comparison Isn’t Perfect
Pain is deeply personal, shaped by genetics, prior experience, anxiety levels, and individual nerve sensitivity. Some women breeze through kidney stones but describe labor as the worst experience of their lives, and vice versa. The 21% of women in the study who rated childbirth as worse aren’t wrong. They had a different experience.
There’s also an emotional dimension that pain scales can’t capture. Labor pain, while severe, comes with the anticipation of meeting a child. Many women describe reframing it as purposeful, which changes how the brain processes it. Kidney stone pain has no such silver lining. It’s pure suffering with no reward at the end, which can make the experience feel even worse than the raw nerve signals would suggest.
Men sometimes assume they “know what childbirth feels like” after passing a kidney stone. That claim frustrates plenty of women, and for good reason. The two experiences involve completely different body systems, different durations, and vastly different emotional contexts. What the data does tell us is that both sit near the top of the human pain spectrum, and neither one should be minimized.