The UTI's tend to come about during pregnancy as the rising hormonal levels (estrogens) make your body more acidic (rather than alkaline, and UTI's require an acidic environment to thrive), as it can kill off some of your probiotic 'good' bacteria - your greatest defense against infections like UTI's thrush, etc.

Cranberry juice/capsules can certainly help, but the most important supplement for you to take are probiotic capsules - you can buy them from the fridge at a health food store - and you should take one every morning before food and last thing before you go to bed. The freindly bacteria will kill off the bad bacteria that is causing the UTI, and help to prevent more in future. The antibiotics are effective at killing bacteria, but they cannot discriminate between good and bad bacteria, and will effectively kill both - that is why, although antibiotics quickly eliminate the UTI , they will also make you more prone to them in future as your probiotic stores will be depleted. That is why the use of antibiotics for UTI's, thrush etc is widely critisied in natural medicine - they treat the symptom, rather than the cause of the problem. The risks of taking antibiotics during pregnancy is widely debated, and studies have found a link between the amount of friendly probiotic bacteria present in newborn infant's digestive tracts with antibiotic use during pregnancy. To clarify - women who take antibiotics during pregnancy have been found to give birth to babies with deficiencies in probiotic bacteria, which is essential for immune support, fighting infection and for optimal digestive health. Rates of colic, reflux, etc are much higher in babies born to women who were administered antibiotics routinely either during labour or after birth during the initial stages of breastfeeding.
The good news is that this is reversable - provided the woman supplements with probiotic bacteria and breastfeeds - as the friendly bacteria will be passed on via the milk. Its ideal to take probiotics throughout your entire pregnancy, if possible, as it can only enhance health.

Increasing your bodies natural Ph level, by eating a alkaline based diet can also help to make your body an unhospitable environment for the bad bacteria to thrive. Google acid alkaline balance to find out more - there are heaps of websites/books etc dedicated to this, and the connection between Ph levels and disease. In the meantime, it would be ideal for you to avoid dairy, refined white grains (white breads, pastas, etc - choose wholegrain varieties instead), sugary processed foods, vegemite, alcohol etc - as these foods feed the infection.
Hope this helps - been there, done that - and this is what truely works!!

XX