Embryo Freezing :
Embryo Freezing is a physical process of converting aqueous solutions into the glassy state on cooling escaping freezing where intracellular ice formation is prevented by the introduction of some agents and very rapid cooling also called Vitrification.
- The embryos are stored in liquid nitrogen at a low temperature of -196degC. Here they are kept in state of suspended animation where every kind of metabolic activity stops. These embryos can be kept in such state for as long as required.
- There are two techniques of cryopreservation, Slow freeze and Vitrification. Vitrified embryos have an excellent i.e more than 90% Freeze- thaw survival rate because of addition of cryoprotectant prior to cooling which acts as antifreeze and also increases the viscosity thereby preventing the crystal formation.
Advantages of Cryopreservation :
- Good alternative in case of initial failure
- Fast & convenient
- Better success rates
Process of FET
- Preparation of Uterus for optimal receptivity
- Administration of pills & 2-3 scans starting from day 2 of the cycle
- Vaginal progesterone 2-3 days before Thawing & Transfer date
- ET process is very simple & similar to earlier one
Fresh vs Frozen Embryo Transfer
Since the introduction of Virtification which ensures more than 90% survival rates its been observed and concluded in many studies that the success rates of Frozen embryos is found to be even better than those with the fresh ones and resulting in
- Increased implantation rates
- Increased live birth rates
- Decreased miscarriage rates
- Lowered risk of pre-term labor
- Healthier babies
“Studies have found that the higher levels of esterogen, enlarged tender ovaries ( Post stimulation ) and altered uterine receptivity after egg aspiration doesn’t present the optimal environment for embryo transfer. In case of FET , actual transfer of embryos happens after a long gap since the ovaries were stimulated with medications therefore the hormones levels have had time to return to normal . This results in more natural conception and also has positive impact on the health of the baby.