Twin: One of two children produced in the same pregnancy. Twins can develop from one ovum (egg) or from two ova (eggs). Twins who develop from a single ovum are called monozygotic or identical twins. They have identical genomes. Twins who develop from two ova that are fertilized at the same time are called dizygotic or fraternal twins. They are nonidentical and have different genomes.
Unfortunately, many women have a small amount of this hormone continuously and if the level gets high enough just before a period, you could get a false pregnancy test result. The best time to use a urine test for pregnancy is three to five days after your missed period.
The lower the number, the more sensitive the test, and the earlier it can detect pregnancy. If you test too soon in pregnancy, even with a sensitive test, the amount of hCG in your urine may not be high enough to detect. Getting a false negative, when a test that says you're not pregnant and you are, can be stressful. The test may be negative for several reasons. You may not be pregnant.