title: Should we be promoting embryo transfer at blastocyst stage?
abstract: Improved laboratory standards and better culture media have made extended culture to blastocyst stage a reality to identify embryos with maximum implantation potential. The strategy of extended culture has become more popular across the world at a time when regulatory bodies have emphasized the need to increase the uptake of elective single embryo transfer, minimize complications associated with multiple births and aim for a healthy singleton live-birth as the preferred outcome in IVF. New data on perinatal outcomes suggest that pregnancies after embryo transfer at blastocyst stage are associated with a higher risk of preterm delivery, large for gestational age babies, monozygotic twins and altered sex ratio compared with those following embryo transfers at cleavage stage. In addition, concerns have been raised of increased congenital anomalies and epigenetic modifications with embryo transfer at blastocyst stage. Twenty-four years on from the first embryo transfer at blastocyst stage, we examine the reasons for extended embryo culture, evaluate the risks and benefits of this strategy and suggest the need to reconsider this policy in the interests of fetal safety.
authors.affiliation: Aberdeen Fertility Centre, NHS Grampian, Foresterhill, Aberdeen AB25 2ZL, UK. Electronic address: abha.maheshwari@abdn.ac.uk.
authors.forename: Abha
authors.initials: A
authors.lastname: Maheshwari
authors.affiliation: Aberdeen Fertility Centre, NHS Grampian, Foresterhill, Aberdeen AB25 2ZL, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Hamilton
authors.affiliation: University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen, UK.
authors.forename: Siladitya
authors.initials: S
authors.lastname: Bhattacharya
mesh_terms: D001723:Birth Rate; D001755:Blastocyst / Q000166:cytology*; D002875:Chromosomes / Q000648:ultrastructure; D002970:Cleavage Stage, Ovum; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods*; D044127:Epigenesis, Genetic; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D061214:Patient Safety; D011247:Pregnancy; D018873:Pregnancy Rate; D012306:Risk; D056826:Single Embryo Transfer; D014430:Twins, Monozygotic
keywords: IVF; blasocyst; embryo transfer; preterm delivery