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Is It Better To Freeze Eggs OR Freeze Embryos

In 1978, the first baby born through in-vitro fertilization (IVF) made headlines in the UK. Now, over four decades later, IVF has become one of the most widely-used fertility treatments worldwide, helping millions of people start families. Throughout this time, IVF technology has evolved significantly, with vitrification – or the freezing of embryos and oocytes – being a particularly transformative advancement. Here’s an overview of how vitrification works, its benefits, and the improvements it has brought to IVF outcomes.

In the early days of IVF, the process typically involved a fresh embryo transfer, where patients would undergo hormonal injections to stimulate egg production, followed by egg retrieval and fertilization to create embryos. These embryos were then implanted shortly after, typically on day three or day five. However, the high hormone levels in the patient’s body after egg stimulation posed a significant risk. Elevated estradiol levels, combined with beta-hCG (the pregnancy hormone), could lead to complications like ovarian hyperstimulation syndrome (OHSS). In severe cases, OHSS could result in life-threatening symptoms, such as fluid buildup in the lungs or abdomen, severe discomfort, and even hospitalization.

Early research suggested freezing embryos for a later transfer could help reduce the risk of OHSS. However, the initial freezing process, known as slow freezing, had limitations. Slow freezing cooled embryos to approximately -16 degrees Celsius, which often resulted in ice crystal formation within the cells. These ice crystals would damage the cells’ structure, decreasing embryo survival rates after thawing and lowering the chances of successful pregnancies.

The introduction of vitrification brought about a rapid and reliable freezing method, improving the safety and effectiveness of embryo preservation. Vitrification is a flash-freezing process that prevents ice crystals from forming within cells, significantly increasing embryo survival rates. By cooling the embryo’s temperature from 37 degrees Celsius to -196 degrees in a matter of seconds, vitrification prevents the formation of ice. Instead, the water inside the embryo’s cells transforms into a glass-like, stable state.

This process uses specialized chemicals called cryoprotectants, which coat and protect the embryo’s cells during freezing. Vitrification has transformed IVF into a safer and more flexible two-step process: initially, creating and freezing embryos, followed by the embryo transfer in a later cycle, once the patient’s hormone levels have normalized. This has minimized the risks associated with OHSS while maximizing the potential for successful pregnancies.

The benefits of vitrification in IVF include:

1. Higher Success Rates: Vitrification has boosted IVF success rates significantly. Whereas earlier techniques yielded success rates around 30-40%, vitrification has raised success rates to approximately 60-65%.
2. Lowered Risks of Complications: By allowing the patient’s hormone levels to stabilize before embryo transfer, vitrification has reduced the risks associated with OHSS.
3. Enhanced Flexibility in Timing: With the ability to freeze embryos safely, doctors can plan the embryo transfer at the optimal time, providing patients with more control over their IVF treatment.

Vitrification has revolutionized IVF, transforming it into a safer, more successful, and more patient-friendly process. By enabling embryo freezing without compromising quality, vitrification has boosted success rates and minimized complications, providing a safer pathway for families seeking fertility support. Today, vitrification is a standard part of modern IVF protocols, helping more patients realize their dream of parenthood.

If you have questions about IVF or vitrification, speak with a fertility specialist to understand your options and ensure the best path forward on your fertility journey.