Many people believe that cranberries can be used to help prevent urinary tract infections. Cranberry is believed to contain an antioxidant called proanthocyanidins. This compound is thought to be a powerful antioxidant. It works by decreasing the adhesion of bacteria to the bladder, making it less likely that the bacteria will colonize and cause an infection.
There is no safety data pertaining to the use of cranberries, cranberry extract, cranberry juice or cranberry supplements during pregnancy. In large quantities cranberry juice can cause diarrhea and other gastrointestinal problems. Cranberries also contain oxalates, the compounds that form kidney stones. If you have history of kidney stones, you should probably avoid cranberries and its derivatives.
As with any medication or dietary supplement, check with your physician before you start any specific regimen.