Selective abortion (multifetal pregnancy abortion)

Abortion in order to achieve a singleton or a lower order multiple birth.


A statistical concept. Data is statistically significant when the differences observed between outcomes or sets of data were not simply due to chance. The smaller a study is, the less confident you can be that findings are significant in this sense of the word.

Single blastocyst transfer (SBT)

When an embryo is cultured in the laboratory until day 5 or 6 and then just one of these embryos (a blastocyst) is transferred to the woman´s womb during a cycle of IVF.

Single embryo transfer (SET)

The transfer of only one embryo into the woman´s womb during a cycle of IVF.


A baby who is carried and born as a single child, not a twin, triplet, etc.

Singleton pregnancy

A pregnancy with only one fetus.

Soft IVF

IVF whereby the woman´s ovaries are only stimulated to produce a small number of eggs, or only one egg, rather than the high numbers normally aimed for in IVF that is based on embryo selection and freezing.

Spontaneous multiple pregnancy

Pregnancy with two or more fetuses after natural conception.