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UTI usually does not affect the urine pregnancy results. The urine pregnancy tests done very early in pregnancy can show you false negative results as the kits are calibrated ones, so unless the hormone levels in urine reach a certain level, they do not show positive results. Urine pregnancy test kits usually start showing positive results after about 20 days post-conception (roughly corresponding to about 1 week after your missed/altered periods). The test should always be done on early morning first urine sample to get accurate results (pregnancy hormone HCG is believed to be in highest concentration in this sample, and you should avoid lot of fluid intake and caffeinated beverages in the night before taking the test). Look out for development of any other new symptoms or persistence of symptoms if pregnancy is suspected. If you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). If pregnancy gets confirmed, consider getting serial HCG levels estimated. Doubling up of the hormone levels in 48-72 hours will show that pregnancy is going on smoothly. If levels are not adequate, then external hormonal supplements would be considered to be started to help you in preventing miscarriage/threatened abortion. An early ultrasound scan done will help to know if pregnancy is intrauterine or ectopic along with confirmation of gestational age and viability. Get started on appropriate (and safe) treatment measures for the UTI detected. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately.
Take care.