Understanding IVF Attrition Rates

One of the most common questions asked by individuals undergoing in vitro fertilization (IVF) is, "How many eggs do I need to make a baby?" The answer is not straightforward, as the number of eggs needed varies significantly based on factors like age, egg quality, and individual medical conditions. Dr. Riwa Sabbagh, a reproductive endocrinologist at Boston IVF, explains the concept of IVF attrition rates and how they impact your fertility journey.

What Are IVF Attrition Rates?
IVF attrition rates refer to the gradual reduction in the number of viable eggs and embryos during the IVF process. As you go through IVF, not every egg retrieved will be mature, not every mature egg will fertilize, and not every fertilized egg will develop into a blastocyst (an early-stage embryo). This natural decline, or attrition, occurs throughout the IVF cycle and is influenced by factors such as age and egg quality.

The Role of Egg Quality and Quantity
Two key factors play a role in determining how many eggs you will need during an IVF cycle:

• Egg Quantity: The number of eggs you have, also known as ovarian reserve, can be measured through tests like anti-Müllerian hormone (AMH) levels and antral follicle count (AFC) via ultrasound. These tests provide a sense of how many eggs are available for retrieval during an IVF cycle.
• Egg Quality: Unlike egg quantity, there is no reliable test for egg quality. Egg quality is closely linked to age—the older an individual is, the more likely the eggs are to have chromosomal abnormalities. This decline in egg quality impacts both the ability to form blastocysts and the chances of achieving a successful pregnancy.

How Many Eggs Do You Need?
The number of eggs needed to result in a live birth depends on several factors, especially age. Here’s a breakdown of how the numbers typically play out during the IVF process if you start with 10 eggs retrieved:

• About 80% of the retrieved eggs are expected to be mature and ready for fertilization. This means that out of 10 eggs, around 8 will likely be mature.
• Of those 8 mature eggs, roughly 30-50% are expected to develop into blastocysts, meaning around 3-4 blastocysts.
• The number of chromosomally normal embryos (which are more likely to result in a successful pregnancy) depends largely on age. For individuals aged 30-35, around 70% of blastocysts are chromosomally normal. In this case, 2-3 blastocysts may be viable. For those around age 40, the percentage drops to around 30%, meaning only 1 blastocyst might be chromosomally normal.

Age and the Number of Eggs Needed
As individuals age, both the quantity and quality of eggs decline, which means more eggs are required to have a good chance of a successful pregnancy. Dr. Sabbagh shared findings from a study conducted at Boston IVF that provide estimates for how many eggs are needed at different ages:

• Under 35 years old: Around 9 eggs are needed to have a good chance of achieving a live birth.
• Ages 35-37: Approximately 11-12 eggs are needed.
• Ages 38-40: Around 18 eggs may be required.
• Ages 41-42: Up to 40 eggs may be needed.
• Over 42 years old: Around 67 eggs may be necessary.

These numbers can feel overwhelming, especially for individuals over the age of 40, but it’s important to remember that reaching these egg counts may take multiple IVF cycles. Boston IVF offers alternative methods and support to help individuals achieve their family-building goals, even if reaching high egg counts is not feasible in a single cycle.

The Importance of Personalization
Every IVF journey is unique, and the numbers mentioned are estimates, not guarantees. Age, medical conditions such as polycystic ovarian syndrome (PCOS), diminished ovarian reserve, or other factors can influence how you respond to IVF treatment. The team at Boston IVF takes a personalized approach to care, adjusting your treatment plan based on your individual needs.

Support Throughout Your IVF Journey
Boston IVF understands that the IVF process can be complex and sometimes overwhelming. As Dr. Sabbagh emphasizes, the goal is to ensure that patients are informed and supported at every step of their treatment. The fertility specialists at Boston IVF will work with you to interpret test results, explain the implications of attrition rates, and create a tailored plan that gives you the best chance of achieving your family-building dreams.

Conclusion
IVF attrition rates highlight the importance of understanding that not every egg retrieved will lead to a baby. The number of eggs needed for a successful pregnancy depends on age, egg quality, and individual health conditions. While these numbers may seem daunting, Boston IVF is committed to guiding you through the process with personalized care and expertise.