What are the causes of urinary tract infection during pregnancy?

Pregnancy complicated by urinary tract infection not only has adverse effects on the mother's body, but may also cause various harms to the fetus. Pregnancy complicated by urinary tract infection may be caused by progesterone, or enlarged uterus, which compresses the ureter at the entrance of the pelvic cavity to form mechanical obstruction.

1. The renal pelvis, calyces and ureters dilate during pregnancy. The placenta secretes a large amount of estrogen and progesterone during pregnancy. Estrogen causes the muscle layer of the ureter, renal pelvis, renal calyx and bladder to proliferate and hypertrophy, while progesterone relaxes the ureteral smooth muscle, weakens peristalsis, and reduces the bladder's sensitivity to tension, resulting in overfilling, incomplete urination, and increased residual urine, creating conditions for bacterial reproduction in the urinary system.

2. The enlarged uterus compresses the ureter at the entrance of the pelvis, causing mechanical obstruction and dilation of the renal pelvis and ureter. Since the uterus is mostly right-handed, the right side is more important.

3. The enlarged uterus and fetal head push the bladder upward, causing difficulty in urination, urine retention, or urine reflux into the ureter.

4. Physiological diabetes is common during pregnancy, and the amount of nutrients such as amino acids and water-soluble vitamins in the urine increases, which is conducive to bacterial growth and tends to cause asymptomatic bacteriuria to develop into acute pyelonephritis. Escherichia coli is the most common pathogenic bacteria, accounting for 75% to 90%. Next are Klebsiella, Proteus, Staphylococcus, etc.