Why do I need to retrieve more than one egg to hopefully have a baby later on?

Since a baby grows out of just one fertilized egg cell, it seems counterintuitive that you’d have to freeze more than one egg to increase your likelihood that your frozen eggs will result in a baby. However, while eggs seem to survive the freezing and subsequent warming relatively well, the actual IVF procedure tends to be a lot less efficient. You can think of the process from freezing an egg to implanting it in your uterus as a funnel that gets narrower:

For instance, you may start off with 17 eggs that are maturing in their follicles on your ovaries. Once the eggs are retrieved from the follicles, not all of them may be fully mature, and sometimes an enlarged follicle may not actually contain an egg. You may end up with 13 mature eggs that are successfully flash-frozen after retrieval. Once you decide to use those eggs, not all of them may survive warming, and you may have only 12 successfully thawed eggs. Up until this stage, you unfortunately have no idea of the quality of your eggs, as there’s no way yet of testing if an egg cell is healthy before its fertilization and early development.

The quality of the eggs (and of the sperm you’re using) comes to a test once you start the actual IVF process: Only 70-80% of your thawed eggs might successfully fertilize (getting you to 8 fertilized eggs in our example), and not all of those embryos will typically grow to be blastocysts during the first five days of development (e.g., you might have only 3 blastocysts). Some of the embryos might stop growing due to genetic abnormalities that would’ve kept them from growing in your uterus as well. Finally, your uterus may reject an embryo that’s implanted and therefore not lead to a live birth.

While all the points at which you could lose eggs sound scary, there’s also some good news:

  • Most eggs are lost during the IVF process, not the freezing and warming. If you have to use IVF to conceive, anyway, then you’ll encounter IVF-related inefficiencies whether you use frozen-thawed eggs or older live eggs. You are likely to have better chances at IVF success using younger (frozen-thawed) eggs, that will typically be of higher number and quality than older eggs.
  • The available data on egg freezing and IVF tend to skew toward women in their late 30s and early 40s, who have been the main users of the procedures. However, if you’re working with younger eggs, you’ll likely have higher chances of success at most steps than what’s reported in the literature.
  • Both IVF and egg freezing techniques continue to improve; if your eggs are frozen for a number of years, research breakthroughs may happen that decrease the likelihood of losing eggs in the IVF funnel even further.

If you’re considering freezing your eggs, check out Ovally for a high-quality, affordable option.

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