The risk of multiples has long been an unfortunate cost of IVF. Since the first test-tube baby in 1978, doctors have been transferring multiple embryos to a mother’s uterus in hopes of achieving one healthy fetus. Back then, doctors had no way of knowing which embryo would be the one, so “people were hedging their bets,” says Dr. Robert Stillman, medical director emeritus at Shady Grove Fertility Center, the largest fertility program in the country. But thanks to improvements in technology, fertility doctors today are much better at selecting healthy embryos to transfer.