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The birth control does not affect pregnancy test results as the pregnancy test kits show pregnancy by detecting hormone HCG which is not present in your birth control. Women have reported getting pregnant even with having the Implanon (due to chances of contraceptive failure). If you suspect chances of pregnancy, or if periods have been abnormal, or if symptoms suggestive of pregnancy (spotting, frequent urination, feeling bigger, bloating etc) are persistent, 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). Get the Implanon removed if pregnancy gets confirmed. Ultrasound scan done will help to confirm gestational age and viability. Be in regular monitoring and follow-up with your treating doctor and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle.
Take care.