Most common cause of UTI in pregnancy:
**Core Concept**
Asymptomatic bacteriuria and urinary tract infections (UTIs) are more common in pregnant women due to physiological changes such as increased urinary frequency, hormonal alterations, and urinary tract dilation. The risk of UTIs is higher in the second and third trimesters.
**Why the Correct Answer is Right**
The most common cause of UTIs in pregnancy is *Escherichia coli* (E. coli), which accounts for approximately 80-85% of cases. This bacterium is a gram-negative rod that typically inhabits the gastrointestinal tract but can ascend to the urinary tract, causing infection. In pregnant women, the increased urine pH and decreased bladder capacity create an ideal environment for E. coli to colonize and cause infection.
**Why Each Wrong Option is Incorrect**
* **Option A:** *Staphylococcus saprophyticus* is a common cause of UTIs in young, sexually active women but is less common in pregnant women.
* **Option B:** *Klebsiella pneumoniae* is a gram-negative rod that can cause UTIs, particularly in patients with urinary tract abnormalities or catheter-associated infections, but is not the most common cause in pregnancy.
* **Option C:** *Pseudomonas aeruginosa* is a gram-negative rod that can cause UTIs, particularly in patients with urinary tract abnormalities or catheter-associated infections, but is not the most common cause in pregnancy.
**Clinical Pearl / High-Yield Fact**
Pregnant women with UTIs are at increased risk of developing pyelonephritis, which can lead to preterm labor and low birth weight. Aspirin therapy should be avoided in UTI treatment, as it can interfere with the effectiveness of certain antibiotics.
**Correct Answer:** C. *Klebsiella pneumoniae*