Pregnancy Rates Analysis 101: Some Basics

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For my first blog session aimed at increasing awareness around fertility treatments and in helping you to analyse the myriad of stuff that gets presented out there, I’ve chosen to review a newspaper article that recently came across my desk, written in the Buderim Chronicle. The original article is attached and just like a tutorial, you can use it as background reading for our discussion today.

030910 ‘Natural’ options yield big results

Now, firstly can I say this is not intended to be a criticism of the newspaper, natural fertility choices or the beautiful town of Buderim, it just happens to be the most recent one of these kinds of stories that I have seen. I could have used any one of hundreds of these kinds of pieces that appear in newspapers or drift around the internet.

Now, to analyse this piece and to help decide whether it has relevance to your fertility situation, you need to be aware of some important statistical concepts (they are not hard, but it would seem that many journalists and health professionals don’t get them). They are:

  1. Numbers matter. There is no value in reporting one person’s story and then expect their story to equate to yours, or thousands of others, in trying to calculate the chance of the treatment in question leading to success. It can make for interesting reading, it can be fascinating or heartbreaking (that’s why journos love human interest stories), but this is of no value in determining the chance of that treatment actually leading to pregnancy. You need many identical cases to compare one kind of treatment with another, and you need maybe hundreds of identical cases in different treatment groups before any difference can be deemed to be statistically significant (more of statistical significance in a future post).
  2. There are two different ways of expressing a chance of pregnancy following treatment. One is thechance per event and the other is the overall chance. Any one menstrual cycle (or a treatment cycle like one IVF cycle) gives one chance in that month only eg if 100 women try one IVF cycle, on average maybe 30 will become pregnant – therefore one IVF cycle has a 30% success rate. The second way of calculating success looks at the overall chance of pregnancy, say by following a particular strategy or treatment over say, 12 months of multiple cycles. This is what you would try to measure when couples try to get pregnant naturally over many months – it’s not the chance per cycle, it’s their overall chance over one year – this is what naturopaths would calculate (although I’ve never seen true success rate tables on their websites). In summary, in comparing percentage rates you should compare “apples with apples”.

So, fellow professors, armed with these simple concepts, let’s return to the Buderim Chronicle…

“ ‘Natural’ Options Yield Big Results…Kellie (surname withheld) is one of a growing number of Sunshine Coast Women successfully turning to natural fertility treatment after suffering two heartbreaking miscarriages and difficulty conceiving for more than one year.” OK let’s stop there. What does a “growing number” mean? Were two women a month doing this before and now there are three? Or were there 1000 women per month previously, and now there are 1999 per month? Numbers matter.

Let’s continue: “Kellie said her miscarriages alerted her to the fact that there was something wrong with her body. ‘I had heard of a friend having success with a naturopath and wanted to give it a try before heading down the fertility specialist/IVF path’, she said.”  Kellie has also ignored the ‘numbers matter’ concept, but in retrospect that’s OK. But why is the journalist and/or the Buderim Meadows Naturopathy Clinic implying that Kellie’s only alternative was IVF? In fact, when I read Kellie’s story, it does indeed seem that she was not as well as she could have been. Gaining weight and eating better seemed to have done the trick, something I would have advised her if she if chose a fertility specialist rather than a naturopath. It’s no secret that underweight women with irregular cycles, abnormal hormone levels as a result and low body mass index in general have higher rates of infertility and miscarriage –here’s just one of hundreds of references.

Nonetheless, the article then tries to compare success rates from two treatment approaches: “We have a 100% success rate with the clients who persist with our program.” Now this is the kind of stuff that gets me angry. So, the naturopathy works even if you have premature menopause and no eggs left? Or if you have completely blocked and scarred fallopian tubes?  Without some kind of “conditions apply” this statement is at best a poor marketing effort (since no one seriously believes it anyway and it decreases the clinic’s credibility). But then we get to the IVF vs naturopathy comparison: “But in general, with totally natural fertility protocols, you can increase your chances of a successful, healthy pregnancy by 70-80% compared with IVF’s 30% success rate”. By the way, what happened to the 100% chance? Now it seems to be 70-80% in general (whatever that means), but the comparison with IVF is unfair:

  1. Because does this mean that your overall chance of conceiving with naturopathy over, say,  one year is 70-80%? What would a couples’ chance of conceiving with multiple cycles of IVF over one year be (remember the IVF stat is per one cycle, this article appears to inappropriately use the two different ways of calculating pregnancy we talked about earlier).
  2. What would a healthy couples’ background chance of getting pregnant be anyway, over one year? I can tell you – 70-80%. So are we comparing healthy couples trying to get pregnant on their own, with healthy couples trying to pregnant with naturopathy? If so, it’s no different.
  3. The statement could mean an increase of 70-80% – ie if the chance was originally 10%, increasing it by 70-80% actually means adding on only another 7-8% , for a new total of 17-18%.
  4. Finally, it is unfair to compare the success rates from IVF with the success rates of those couples trying on their own who don’t need IVF – IVF is undertaken by couples with significant medical fertility problems.

In summary, then, this article does not help a women with infertility decide whether naturopathy is firstly of any value or secondly better than fertility treatments like IVF, simply because it doesn’t make any relevant statistical comparisons and it doesn’t compare “apples with apples”.

I hope you have found this a good first start in helping you weigh information up. I’ll post more soon – but in the interim, try using some of your new-found skills when you are trawling the internet, or next see some “breakthrough” article in the papers or on TV. If you wish, post some examples with your analysis!

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