Birth Control is used to prevent pregnancy. In general, it is used to prevent a woman from ovulating, thus making it impossible for sperm to fertilize an egg because there is no egg present. While birth control is 99 percent effective in most cases, human error is often made ineffective. If you find yourself needing to take a test while on any birth control, go ahead and take it. One of the device nexplanon is used for birth control i.e. implanted in the woman's upper arms. You can know more about nexplanon device via https://embrywomenshealth.com/nexplanon-specialist/.
A pregnancy test is designed to detect the pregnancy hormone in your urine. It appears in your urine after you become pregnant. This means you will have experienced the conception when the egg meets the sperm and become fertilized. You will also have experienced the journey of your eggs fertilized long journey fallopian tubes and implant itself in your uterine wall.
Your body will start to produce the pregnancy hormone hCG until your egg in the uterine wall. Since then, it takes a week or more for your hCG levels to be high enough to detect the pregnancy test.
Taking birth control should prevent the release of an egg. However, after that failed, there is no birth control you can do. It can not be fertilized eggs and fetuses harm your unborn child because it was not what it was designed to do.