[Elective single embryo transfer in assisted reproduction].

Area of Science:

• Reproductive Medicine
• In Vitro Fertilization (IVF)
• Clinical Embryology

Context:

• Norway's assisted reproduction regulations permit IVF clinics autonomy in embryo transfer numbers.
• Historically, embryo transfer numbers were reduced, but twinning rates remained high, with 27.5% multiple births in 2002.
• To mitigate high multiple pregnancy rates, elective Single Embryo Transfer (eSET) was implemented in November 2004 for select patients.

Purpose:

• To evaluate the effectiveness of eSET in reducing multiple pregnancies within a specific patient cohort.
• To compare pregnancy and twinning rates between eSET and double embryo transfer (DET).
• To assess the potential for cryopreservation and cumulative pregnancy rates with eSET.

Summary:

• A study of 644 cycles using eSET in patients under 35 with top-quality embryos showed a 33% live birth/ongoing pregnancy rate.
• This compares favorably to 23% in cycles with two embryo transfers, with a minimal decrease in overall pregnancy rate (32.4% vs. 34%).
• The twinning rate significantly decreased to 18.1% with eSET, and 60% of patients had embryos available for cryopreservation.

Impact:

• eSET implementation successfully reduced the twinning rate in assisted reproduction.
• The findings suggest that establishing a national eSET policy could optimize the balance between cumulative pregnancy rates and twinning rates.
• Further refinement, such as adjusting the age limit for eSET, may further improve outcomes and reduce multiple pregnancies.