There is no need for a male partner for the egg freezing process. However, men can freeze their
sperm for any future use. The most common fertilization method is cryopreservation. During this
process, oocytes and embryos are frozen under low pressured liquid nitrogen. The cold
conditions can freeze them easily. Then, we manage it with vitrification. Vitrification is a
process where we prevent the liquid from converting into solid, as the highly concentrated
embryos have viscosity. The overall process is effective for assisted reproduction
How the process works
Here’s a simplified breakdown for women and men.
For women – Egg (oocyte) cryopreservation
- Ovarian stimulation: Hormonal injections stimulate the ovaries to produce multiple mature eggs (oocytes).
- Egg retrieval: A minor procedure under sedation to harvest the eggs from mature ovarian follicles.
- Freezing (vitrification): Rather than the older “slow-freeze” method, modern labs use vitrification: ultra-rapid cooling with high concentration protectionists to avoid ice-crystal formation within the cell.
- The term “vitrification” is derived from the Latin for glass (“vitrum”) because the water turns into a glass-like solid state rather than forming ice crystals.
- This rapid freezing helps better preserve cell integrity and yields higher survival after thawing compared to slow freezing.
- Storage: The vitrified eggs are stored in liquid nitrogen (typically at around −196 °C) until the individual is ready to use them.
- Thawing and use: When ready, the eggs are warmed, rehydrated, fertilized (typically via intra-cytoplasmic sperm injection – ICSI) and then transferred into the uterus like in a standard IVF cycle.
For men – Sperm cryopreservation
- The process is simpler: semen collection, addition of protectionists, controlled freezing or vitrification in some labs, storage until needed.
- Unlike eggs, sperm freezing has been routine for decades, and the technique is well established.
Why vitrification matters
Since eggs and embryos are particularly vulnerable to damage from ice crystals (because of their size and water content), vitrification has been a game-changer.
Here are some key advantages:
- Much higher survival rates after thawing.
- The “glass-like” state avoids ice crystals that can damage cell structure.
- More flexible scheduling and better outcomes in many cases.