How Urine Changes Throughout Pregnancy
Pregnancy hormones, increased blood flow to the kidneys, and the growing uterus all influence how often you urinate and how your bladder feels during pregnancy.
“Women with multiple pregnancies or underlying health conditions such as high blood pressure, diabetes, pre-pregnancy kidney issues, sickle cell disease, or especially sensitive bladders might notice more pronounced changes,” says Shivika Trivedi, MD, an assistant professor and obstetrician-gynecologist at UChicago Medicine in Illinois.
These shifts can start early and continue throughout pregnancy.
First Trimester Changes
As early as the first trimester, many women notice they need to urinate more frequently, says Jonathan Schaffir, MD, a clinical professor and an obstetrician-gynecologist at the Ohio State University Wexner Medical Center in Gahanna, Ohio.
“Part of this is due to the increased rate at which blood flows through the kidneys,” he says. “There’s actually more urine being produced.”
The need to pee more often is also due to the expanding size of the uterus, says Dr. Schaffir. “During the first trimester, the uterus is competing for space in the pelvis where the bladder is, so bladder capacity may be diminished,” he says.
It’s a good idea to increase your fluid intake when you’re pregnant to accommodate the increased amount of blood in the bloodstream, says Schaffir. “For women who are drinking more liquids, urine may become more dilute,” he says.
Second Trimester Changes
As the uterus grows upward into the abdomen, pressure on the bladder may temporarily lessen. And while there’s still more urine being produced, the rate tends to level off at this point, says Schaffir.
Between that and the uterus’s new position above the bladder in the abdomen, there may be some reprieve from frequent bathroom trips, he says.
Third Trimester Changes
You may notice a little urine leakage during your last trimester. Two hormones that rise in pregnancy, relaxin and progesterone, cause the relaxation of muscles, ligaments, and blood vessels, including those in the bladder, says Trivedi.
“That allows more urine to be held in the urinary tract itself and also leads to relaxation of the pelvic floor muscles that can cause leakage of urine with a cough, sneeze, or laugh,” she says.
This relaxation also allows increased fluid to pool in the legs, which then reenters the bloodstream when a pregnant person lies down, leading to increased urine production and increased nighttime urination, says Trivedi.
In the final months of pregnancy, the uterus (now holding a larger fetus) puts a lot of pressure on the bladder, so individuals may have difficulty holding much urine in the bladder, which can mean going to the bathroom more frequently again, says Schaffir.
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