Urinary tract infection during pregnancy

By trimester

Weeks 1–13

1st trimester

Routine prenatal care includes a urine culture early on, because bacteria can be present with no symptoms at all. That early screen is the reason many first-trimester infections get picked up before you would ever notice them.

Weeks 14–27

2nd trimester

The ureters keep widening and urine keeps moving more slowly, so a simple bladder infection has more room to travel upward. New burning or urgency is worth reporting the day it starts.

Weeks 28–birth

3rd trimester

The uterus presses hardest on the bladder now, and frequent urination is normal on its own. What separates ordinary frequency from an infection is pain, fever, or flank pain, and those belong in a phone call.

What does the evidence show for urinary tract infection?

• Pregnancy hormones relax the smooth muscle of the ureters and the enlarging uterus compresses the bladder, so urine sits longer and bacteria have more opportunity to climb. 1
• UTIs affect about 10 to 18 percent of pregnancies, with asymptomatic bacteriuria in 2 to 10 percent, cystitis in 1 to 2 percent, and pyelonephritis in 1 to 2 percent. 1
• About 25 percent of asymptomatic bacteriuria cases that go unaddressed progress to a symptomatic UTI during pregnancy. 1
• Screening with a urine culture is recommended in pregnancy, with one common approach taking the sample toward the end of the first trimester and repeating a culture afterward. 2
• Among 158 pregnancies with a kidney infection, 13.3 percent developed sepsis, 11 percent delivered before 37 weeks, and 7.6 percent needed high-dependency or intensive care, which is why early recognition matters. 3

When should I call my provider about urinary tract infection?

A bladder infection can move up into the kidneys, so call your provider the same day for a fever of 100.4°F (38°C) or higher, shaking chills, or pain in your back or side below the ribs, particularly alongside nausea, vomiting, or a general sense of feeling unwell. A racing heartbeat or lightheadedness on top of those symptoms can mean the infection is spreading into your bloodstream, which needs prompt evaluation rather than a routine appointment. New or worsening burning, urgency, or pelvic pressure is also worth a same-day call, since catching a bladder infection early, before it reaches the kidneys, is what keeps this escalation from happening in the first place. Trust your read on your own body. If something feels off beyond the list above, please consult your healthcare provider rather than waiting it out.