More importantly, fetal complications include prematurity and the resulting increase in infant morbidity and mortality. Furthermore, the rearing of high order multiples creates physical, emotional and financial stress for the family with a reported increase in the incidence of maternal depression and anxiety. For these reasons, reducing the number of high order multiples has become an essential goal of most successful IVF programs.

Two relatively new developments in the art and science of IVF appear to significantly decrease the need to transfer a large number of embryos and therefore, offer the promise of decreasing the incidence of high order multiple pregnancies. In 1990, preimplantation genetic diagnosis (PGD) became a reality. Embryos created through IVF can now be tested for age-related genetic abnormalities. This screening allows the clinician to transfer fewer PGD screened embryos in women 35 years of age and older, while still maintaining high rates of pregnancy.

The second significant development has been the ability to keep embryos in culture for five days (blastocyst stage) instead of two or three days (cleavage stage) prior to transfer. Blastocysts are more likely to implant and lead to pregnancy. Therefore, the fewer blastocysts (usually only two) need to be transferred in order to maintain good pregnancy rates.