Should we be promoting embryo transfer at blastocyst stage?

Area of Science:

• Reproductive Medicine and Embryology
• Perinatal Outcomes
• In Vitro Fertilization (IVF)

Background:

• Advances in laboratory standards and culture media enable extended embryo culture to the blastocyst stage.
• Extended culture is increasingly adopted globally, aligning with regulatory emphasis on elective single embryo transfer (eSET) and singleton live births.
• The goal of extended culture is to identify embryos with the highest implantation potential.

Purpose of the Study:

• To examine the rationale behind extended embryo culture to the blastocyst stage.
• To evaluate the associated risks and benefits of blastocyst stage embryo transfer.
• To reconsider the policy of extended embryo culture in light of fetal safety concerns.

Main Methods:

• Review of current literature and data on extended embryo culture.
• Analysis of perinatal outcomes following blastocyst versus cleavage stage embryo transfer.
• Examination of concerns regarding congenital anomalies and epigenetic modifications.

Main Results:

• Pregnancies resulting from blastocyst transfer show increased risks of preterm delivery, large for gestational age infants, and monozygotic twins compared to cleavage stage transfer.
• Concerns exist regarding potential increases in congenital anomalies and epigenetic alterations with blastocyst stage transfer.
• Despite improved implantation potential identification, safety data warrant careful consideration.

Conclusions:

• Extended embryo culture to blastocyst stage, while improving embryo selection, may be associated with adverse perinatal outcomes and developmental concerns.
• The benefits of identifying high implantation potential embryos must be weighed against potential risks to fetal safety.
• A re-evaluation of the widespread adoption of extended embryo culture policies is necessary to prioritize healthy singleton live births.