Treat them. They are important to treat, because an untreated UTI is much more likely to become pyelonephritis (kidney infection) when you are pregnant. This is because the uterus puts pressure on the ureters (kidney to bladder), impairing bladder drainage. The right kidney is at greater risk than the left.
Avoid. Treat any UTI. All utis during pregnancy should be treated to avoid kidney infects which are bad news. Thus test if suspected, ie if urine smells or burns or u have flank pain. Pregnancy makes u >liable to utis.Try to avoid by showers rather than baths. No bubble-bath. Urinate after sex. Separate thighs widely whilst urinating. Drink plenty of water. Don't hold back if bladder feels full.