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.
Sometimes, a woman will have extremely high levels of hCG in her blood when she is not actually pregnant. This can lead to a false positive pregnancy test. Some of the reasons for high hCG levels can be a tumor, ovarian cancer, a multiple pregnancy, blood or protein in the urine, or certain medications. Too low hCG levels. Sometimes a woman will have low or even negative hCG levels. There can be a few reasons for this.