1 in 8 Pregnancies Involve Twins

Though it sounds like a Stephen King title, vanishing twins are actually quite common. Researchers estimate that 1 in 8 pregnancies involve twin fetuses, yet only 1 in 80 pregnancies actually ends in the birth of twins [source: Goldman]. What happens to all those unborn twins? They die very early in the pregnancy and are simply reabsorbed by the mother's body. Spotting in the first trimester can be an indication of this occurrence. [1]