It is common knowledge that assisted reproduction methods, such as intrauterine insemination (IUI) and in vitro fertilization (IVF), when successful, often result in multiple pregnancy. Some wonna-be-moms, in fact, want to have twins or triplets, especially those who have tried to conceive for a long time—after all, having more than one baby at the same time seems to compensate for the many months or years lost in waiting. Doctors, however, frown at such possibilities. The optimal outcome of an assisted reproduction, they say, is a singleton pregnancy.