Overview

Embryo cryopreservation preserves embryos at ultra-low temperatures for future use. During IVF, multiple embryos are often created; those not transferred can be frozen and used in future cycles. This significantly improves cumulative success rates from a single egg collection.

Why Freeze Embryos?

• Surplus embryos from IVF — most common reason
• Freeze-all strategy — recommended when OHSS risk is high, uterine environment not optimal, or awaiting PGT results
• Fertility preservation before cancer treatment (with a partner)
• PGT — embryos biopsied and frozen while awaiting genetic results

Vitrification

The modern standard is vitrification — ultra-rapid freezing (>20,000°C/minute) that prevents ice crystal formation. Embryo survival after thaw: >95%. Blastocyst-stage freezing (day 5–6) is preferred for better selection.

Frozen Embryo Transfer (FET)

1. Endometrial preparation with oestrogen then progesterone
2. Ultrasound monitoring — lining must reach ≥7mm
3. Embryo thawed on morning of transfer
4. Quick transfer via thin catheter — no anaesthesia
5. Pregnancy test 10–14 days later

Success Rates

FET success rates now equal or exceed fresh transfer rates, as the uterine environment is undisturbed by stimulation hormones. Success depends primarily on the woman's age when embryos were created and embryo quality.

Have surplus embryos or want to plan ahead? Book a consultation today