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Cumulative Odds of Pregnancy with IUI/IVF

Example: If each cycle has a 25% chance of pregnancy, what are your odds of getting pregnant in 3 attempts?

Before you take a gamble on something as expensive and demanding as IVF or IUI, it's only natural to want to know the odds of getting pregnant. To be realistic, you need to think about the odds of multiple attempts, since the odds are against getting pregnant on the first try.

Here are the statistical cumulative odds for getting pregnant over a number of cycles, given the odds of success on a single attempt. I have included a graph to show the trends, but it may be easier to check the chart below. Find the odds of success for a single cycle along the left, then move to the right to see how the cumulative odds increase with each additional cycle. Scroll down to read about what the cumulative odds mean.

Cumulative odds in IVF or IUI

  1 2 3 4 5 6
5% 5.0% 9.8% 14.3% 18.5% 22.6% 26.5%
10% 10.0% 19.0% 27.1% 34.4% 41.0% 46.9%
15% 15.0% 27.8% 38.6% 47.8% 55.6% 62.3%
20% 20.0% 36.0% 48.8% 59.0% 67.2% 73.8%
25% 25.0% 43.8% 57.8% 68.4% 76.3% 82.2%
30% 30.0% 51.0% 65.7% 76.0% 83.2% 88.2%
35% 35.0% 57.8% 72.5% 82.1% 88.4% 92.5%
40% 40.0% 64.0% 78.4% 87.0% 92.2% 95.3%
45% 45.0% 69.8% 83.4% 90.8% 95.0% 97.2%
50% 50.0% 75.0% 87.5% 93.8% 96.9% 98.4%

Back to the example I gave above: If each cycle has a 25% chance of pregnancy, what are the odds of getting pregnant in 3 attempts? The answer is 57.8%. (On the chart, find the row with 25% on the left, then move to column 3.)

Understanding Cumulative Odds

What, exactly, do these odds mean? In the example, it does NOT mean that after 2 failed cycles, your odds jump to 57.8% for the 3rd cycle, because the odds are constant at 25% per cycle. What it actually means is that if 100 women made attempts at 25% per cycle, after 3 cycles 57.8% of the women would be successful.

Finally, it's important to realize that statistics are just a model, and while it's useful to try to predict the future, statistics aren't real life. The odds of success of any single cycle depend on many different factors, and the odds can change for every attempt.

Note: Odds are calculated as a cumulative binomial probabability distribution.