Natural Conception after Adoption and Assisted Reproduction Treatment

Today at work I was putting together a presentation on “What is correlation?” (I know, my work is full of excitement and such geekery 😎 ), and I came across an interesting example of ‘illusory correlation’ from the infertility world that I thought I would share with you all.  I was about using it as an example in my presentation.

Have you ever heard someone say

“Adoption increases the chance of an infertile couple getting pregnant naturally?”

Many people have heard or say this, and many can tell you a story of someone they know/know of that this happened to.  The rationale behind this can be hypothesised as:

Once the pressure is off and the couple is less anxious, it will happen naturally.

But how true is that?

Apparently it turns out there is NO empirical evidence to support such a hypothesis.  Research (from Resolve) has shown that the percentage of women who become pregnant without adopting is no different to the percentage of women who become pregnant without adopting.  What this means is that, while a small percentage of people who were having difficulty getting pregnant do not get pregnant after adopting a child, these are likely the same people who would have gotten pregnant after having difficulty, even without the adoption.  It has nothing to do with the adoption.

So why do so many people believe this myth?  Because many people can tell you of a story of someone they know that this happened to.  But the thing is, most people can only tell you ONE story.  And they don’t tell you all the stories they know about the infertile couples that adopted a child and didn’t get pregnant naturally afterward.  The examples of where it did happen are salient to them, perhaps because they remember thinking to themselves “This couple is going to have two babies within a few months of age of each other!”  What happens when something is salient – or when it produces a vivid memory – is that people tend to overemphasize the likelihood of its occurrence.  And they give it a lot of attention.

This is known as vividness bias.

The vividness bias is supported by what’s often referred to as an illusory correlation – the impression that two variables are related when in fact they are not.  In this example, because of one or two very salient or vivid examples, many people believe that there is a relationship between adoption and getting pregnant, when in reality, there is not.

(Extracted from: Intentional Interruption: Breaking Down Learning Barriers to Transform By Steven Katz and Lisa Ain Dack)

Similar to the case made for getting pregnant naturally after adoption, you may have heard a similar argument for couples who stop assisted reproduction and get pregnant naturally afterwards.  There is research that was published in 2012 that found that 17% of women who became pregnant, and gave birth, from IVF treatment, became pregnant again naturally (NB….within 6 years!).  For those women who were unsuccessful with IVF, 24% became pregnant naturally after stopping infertility treatment.

Other recent research has found that 16% of infertile women conceive naturally after stopping treatment (within 13 years!).  And by the way, let us not forget that a fertile couple’s chance of conception is 20-24% for every menstrual cycle!  So that 16% statistic still SUCKS.  In addition, the original cause of a woman’s infertility made a difference as to the chance of achieving a successful natural pregnancy after IVF – if the infertility was due to uterine, cervical or ovarian problems, endometriosis or infertility in their male partners, the women had a significantly greater chance of achieving a successful natural pregnancy after stopping IVF.  However in comparison, if the couple’s infertility was ‘unexplained’ or the problem was with tubal pathology, her chances of a natural pregnancy decreased 😦

So there are many illusory correlations out there in the infertility world.  And now you know how to respond to people that say to you:

“ohhh you will get pregnant naturally after adopting/stopping treatment, that happened to my friend/friend of friend”

you can reply

“……the evidence is contrary, my dear, and you are suffering from vividness bias”

It’s a whole lot politer, and factual, than – “F*#$ you”.

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Research shows that age is not correlated with fertility…um OK

I’m back on my data hunt for my course project to develop a web app…and I came across a research paper that explored factors associated with fertility in a small district in India*.  The abstract of the paper begins with:

“This paper focuses on the cause and effect relations on human fertility. Here fertility is used as the number of children ever born for a woman….”

Alarm bells rang as soon as I see ’cause and effect….’.  But I was intrigued, so I read on.  The factors that this study looked at were ‘natural factors’ (including age of woman, age of woman at marriage, religion and type of family) ‘economic factors’ (including employment of woman and spouse, income of woman and spouse) and ‘knowledge factors’ (including education of woman and spouse).  I should now mention that this is clearly NOT a piece of medical research, rather came from a journal of anthropology.  Studies that look at non-medical factors can be revealing never-the-less, so here we go…
I loved the result that the more educated a woman and her spouse were the fertility rate lowered.  Basically you can possibly turn this around and say that the less educated you were the more likely you were to have children.  I think we can guess why.  But it is the way that the report concludes which makes it sound rather amusing…
“Conclusion: Higher employment, higher income of both husband and wife and nuclear family system could bring the reduction in the fertility level of the women in Kanyakumari district”

CORRELATION DOES NOT EQUAL CAUSATION – BAHHHHHH

I know that this research paper was probably trying to assess what causes the high birth rate in this particular district, but I think the translation and the way the conclusions have been made make this a paper a funny read if you are into that kind of geekery.  So Ladies – lose the jobs, dumb up your brain cells and knock a few out of your husband too, and don’t worry, age is not correlated with fertility, that is if we want to learn some lessons from Kanyakumari district!

Oh yes and here is another one of my favourite xkcds.

Cancer Causes Cell Phones – Duh!

* K. Senthamarai Kannan* and V. Nagarajan, “Factor and Multiple Regression Analysis for Human Fertility in Kanyakumari District“. Available at: http://www.krepublishers.com/02-Journals/T-Anth/Anth-10-0-000-08-Web/Anth-10-3-000-08-Abst-PDF/Anth-10-3-211-08-416-Kannan-K-S/Anth-10-3-211-08-416-Kannan-K-S-Tt.pdf