ABSTRACT
The high incidence of multiple pregnancy is a major side effect of assisted reproductive
technology that has recently given rise to justified criticism from different sides.
The reasons for the high incidence of multiple pregnancies are discussed and a brief
review is given of the steps that have been proposed to solve or at least reduce the
problem. In this article, attention is particularly focused on the prevention of twin
pregnancies because in terms of perinatal morbidity and associated costs, they outweigh
the effect of high-order multiple pregnancies when expressed in absolute figures.
The only efficacious measure to reduce the incidence of twin pregnancies is a policy
of single-embryo transfer. We report on our experience with elective single-embryo
transfer in good prognosis patients (age <37 years, first two in vitro fertilization
(IVF) cycles and at least two embryos of high quality). About one-third of the couples
meeting these criteria agreed to have a single embryo transferred, at least during
their first IVF cycle. Pregnancy rates in women who had an elective single-embryo
transfer (more than one high-quality embryo available) were only slightly lower than
those in the group with elective double (i.e., more than two high-quality embryos
available) transfer (37.9 vs. 40.0%) but the incidence of twins was 0.0 versus 27.1%.
This strategy resulted in a substantial decrease of the twin pregnancy rate from 27.0
to 14.9%, without affecting the overall pregnancy rate. The conditions that are to
be fulfilled before this policy can and will be applied on a large scale are discussed.
KEYWORD
ART - twin pregnancy - prevention - single-embryo transfer
