Now that the United States has imposed restrictive guidelines on in-vitro fertilization (IVF), fewer twins, triplets or multiple sets of babies are born via IVF. Previously, doctors would implant numerous embryos in a woman and this increased the chances of her having more than one baby. However, as of 1998, the United States has discouraged the implantation of more than 3 embryos at one time. Since then, the percentage of triplets born through the IVF method has decreased from 48 percent in 1998 to 32 percent in 2011.
~New York Daily, 5/12/2013