Selective reduction

[4] Selective reduction was developed in the mid-1980s, as people in the field of assisted reproductive technology became aware of the risks that multiple pregnancies carried for the mother and for the fetuses.

[10] While the data is weak, due to the small sizes of studies and the lack of randomized controlled trials, as of 2017 it appeared that when short term perinatal outcomes in multiple pregnancies reduced to twins are compared to those of non-reduced triplets, there were fewer deaths among the babies born to mothers who underwent reduction, the twins were born later and were less likely to be premature, and had higher birthweight.

[11] Generally selective reduction reduces the risk of preterm birth, leading to better outcomes for both mothers and the newborns.

[5] Selective reduction was developed in the mid-1980s, as people in the field of assisted reproductive technology (ART) became aware of the risks that multiple pregnancies carried for the mother and for the fetuses.

[7] A set of ethical guidelines was developed in collaboration with a bioethicist from the National Institute for Health and was published in 1988; it justified reducing pregnancies with more than three fetuses to two or three.

[7][13] Over time, more and more women in the developed world sought to become pregnant when they were older, having the first child when they were over forty years old.

These requests increasingly came from women pregnant with twins due to advances in the field of ART which made massively multiple pregnancies rarer.

Monoamniotic triplets, a very rare condition where the triplets share a single placenta, seen on ultrasound. Because a single placenta has difficulty supporting multiple fetuses, in such cases a selective reduction to improve the likelihood of survival for the remaining fetus or fetuses may be indicated. [ 1 ] [ 2 ]
TRAP syndrome . On the left, an acardiac twin which lacks both a heart and head. On the right, the "pump twin" which supplies the acardiac twin with blood. A selective termination of the acardiac twin reduces the risk of death of the pump twin.