IVF by the numbers

Jessi and I can be very analytical people. We made and used extensive spreadsheets to help us with other life-altering decisions. Spreadsheets have helped us choose an internship and a post-doc position, and manage our budgeting system.

To help us determine how many eggs we were comfortable allowing them to fertilize, I knew that I wanted the hard numbers for the probability distribution of transferable blastocysts for each possible number of eggs. We happened to be on vacation, away from the internet, at the time, so I wrote a script to calculate them for us.

Here's the data for fertilizing one, two, and six eggs (see all):

1 eggs in, 1 blastocytes out
  probability (exactly 1): 30%
  cumulative probability (at least 1): 30%
1 eggs in, 0 blastocytes out
  probability (exactly 0): 70%
  cumulative probability (at least 0): 100%

2 eggs in, 2 blastocytes out
  probability (exactly 2): 9%
  cumulative probability (at least 2): 9%
2 eggs in, 1 blastocytes out
  probability (exactly 1): 42%
  cumulative probability (at least 1): 51%
2 eggs in, 0 blastocytes out
  probability (exactly 0): 49%
  cumulative probability (at least 0): 100%

6 eggs in, 6 blastocytes out
  probability (exactly 6): 0%
  cumulative probability (at least 6): 0%
6 eggs in, 5 blastocytes out
  probability (exactly 5): 1%
  cumulative probability (at least 5): 1%
6 eggs in, 4 blastocytes out
  probability (exactly 4): 6%
  cumulative probability (at least 4): 7%
6 eggs in, 3 blastocytes out
  probability (exactly 3): 19%
  cumulative probability (at least 3): 26%
6 eggs in, 2 blastocytes out
  probability (exactly 2): 32%
  cumulative probability (at least 2): 58%
6 eggs in, 1 blastocytes out
  probability (exactly 1): 30%
  cumulative probability (at least 1): 88%
6 eggs in, 0 blastocytes out
  probability (exactly 0): 12%
  cumulative probability (at least 0): 100%

Our ideal number of transferrable blastocysts is just one so that we would not need to freeze any extra embryos. On the other hand, we were also mindful of the statistical risk of no viable blastocysts, and knew we needed to avoid extra, unnecessary physical and emotional toll on Jessi’s body in this process that would occur from several harvesting cycles with no viable blastocysts. We were also very concerned about the total number of eggs we attempted to fertilize aligning with how many children we felt that we could actually imagine having, should all of them make it through the entire process.

Our Reproductive Endocrinologist relayed a story to us about a couple she'd worked with who were only willing to fertilize two eggs at a time, and they did not get a transferrable blastocyst in three cycles. A typical egg harvest in someone Jessi’s age tends to produce about ~15-20 eggs, ready for fertilization. When we started talking limited fertilization she started by offering us 10. However, in the end, we felt we could not do any more than six in order for us to fully respect each potential of life, as we did not feel that we could feasibly imagine having more than six children.

Analytics only gets you so far. It helps you understand the numbers and the apparent chances, but ultimately, everything is in God's hands. It is God, not IVF, that creates life. He's got the whole world in his hands, right? There's nothing that we're taking away from God by combining the gametes in vitro, rather than naturally.

The first big take-away here is that life is precious and a gift from God. As we have stated before, we both believe that life begins at fertilization, a belief that we both took very seriously in each decision we made. We cherish each life that God chooses to create through this process, and also know that we are likely staring into the face of a lot of loss. We've already had to say goodbye to two precious little ones, and we are likely looking at saying goodbye to several more before we get to say hello to one on this side of Heaven.

The second is that we spent a ton of time in prayer, asking for His peace in our hearts and minds going forward in this process. He gave us hearts to love, to feel, to care, to grieve. He also gave us minds to think, to reason, to compare. So we're all in, on His plan as He reveals it to us.