Is twin pregnants often miscarry and why?

Pregnancy multiples: Twins, Triplets, etc have a slightly higher rate of pregnancy loss initially due to genetic malformations and later due to uterine "crowding" resulting in premature labor/delivery.

Not unless: drugs that induce ovulation are used. Miscarriages have relationship to future chances of twin pregnancy

Hope my answer helps: Twins are 2 embryos implanting. The risk of miscarriage with one embryo implanting ia approximately 15% and with 2 embryos this risk is bound to double. In addition, some of the twin pregnancies are from cleavage of 1 embryo that is associated with errors such as unequal DNA material in the 2 embryos. This results in miscarriage in most instances as a protective mechanism. Good Luck!