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Common IVF Success Rate Misunderstandings

A blog by Kym Campbell, September 23, 2015

While readily available, IVF statistics are a treacherous path for couples trying to make informed decisions about their IVF treatment options. The potential for misunderstanding and subsequent poor decision making is ever present without a clear understanding of what various statistics mean. Here are four of the most common traps to avoid.

1. Pregnancy Rate vs. Live Birth Rate
While this one seems almost too obvious to be necessary, people (including me!) still get caught confusing pregnancy rates for the probability of having a baby. Almost all IVF clinics will proudly publish their pregnancy success rates, and ironically they all seem to perform significantly better than the national average, because getting you pregnant is their core business. But pregnancy is only a part-of-the-way milestone, and tragically, it is a fact of “trying” that many pregnancy journeys end prematurely to the bereavement of the would-be parents.

What couples really want to know are the chances of having a baby, and to find these results you need to look at “live birth rate”.

2. The Fallacy of the Denominator
It is critical that you understand the denominator used in any IVF success rate because if you get this wrong, you’ll think your odds are better than they actually are. The two most commonly reported success rates are reported on either a per cycle, or a per embryo transfer basis. Because between 6-20% of cycles are cancelled (depending on one’s age), the success rate based on an embryo transfer is always higher than that of a cycle.

Given that the majority of both the discomfort and expense of IVF occurs during egg retrieval, the per cycle rate gives you a better indication of how many cycles you’re likely to need and hence how much your treatment is likely to cost.

3. A Risky Way to Improve Results
If you are a fertility clinic, one of the most effective ways to improve your success rates is to transfer more embryos at a time. This is risky business however, as doing so also increases the chance of multiple births. Hence when comparing different sources of success rates, it is also important to ensure the figures are based on the same “average number of embryos transferred” otherwise you might be comparing apples with oranges.

4. The Elephant in the Room
The one success rate you are unlikely to see advertised at a fertility clinic is the percentage of patients that have a baby over multiple cycles, instead of just one. Ironically, this is also probably the most important number for anyone considering IVF.

The statistic that tells you the answer to this question is the “cumulative probability”, which means the chances of a woman having a baby after multiple IVF attempts.


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