Babymaking Science and Feminism: The Science Bit

Katielase (she of brilliant blog The Molecular Circus) wrote us a belter of a post this morning about the importance of understanding why your body does what it does, and that if women knew why it was harder to get pregnant the more they age, then they’d have the power to make better-informed decisions to do with their body, and  subsequently their lives.

And here it is.  Here’s the why.  Replete with vivid analogies and a great big dose of humour.

Over to you, Katie:       

Halfway through writing my soapbox post on women not having access to scientific information about their baby-making business, I realised that it would be silly to be so frustrated and take no action. I genuinely believe that all people have the right to make informed decisions about what they do with their baby-making bits. To be honest, I care not what you do with them, but I do care that the information is accessible and readily available, that way people can ignore it or react to it, or whatever, but they have the CHOICE. So here we are, some science about reproductive ageing in women.

The majority of human cells have 23 pairs of chromosomes (46 chromosomes in total), and when you were a weeny tiny fertilised egg, you started off life as a bundle of cells, each of which had these 23 pairs. You got this DNA from your parents: one of each chromosome pair from your Mum, and one from your Dad, giving you your total of 46 chromosomes. Then, your tiny bundle of cells replicated and grew and became a tiny amazing human, with lots of cells, all of which had 46 chromosomes. Except, not quite all of them do… 

One of the exceptions to this 46-chromosome rule are sperm and egg cells. These only need one of each pair, so that when they join together, the resulting embryo cells have the full 46. The process of producing these haploid cells is known as meiosis. Meiosis is both intricately complex and elegantly straightforward. It involves a cell splitting itself in two, and sending half the DNA to one side and half to another. I always imagine the cell during this process as a giant school sports hall, with kids running to one end or the other. Only, it’s really really important that the right kids run to the right place, blue team on one side, red team on the other. There’s no use having kids who are easily panicked by running, like me as a child, getting lost and ending up in the wrong place. Your DNA is the blueprint for you, it’s not going to work if you have several copies of the gene for having blue eyes, and no copies of the gene for the enzyme that digests starch. You’re a super complicated machine, you need all your bits in the right places.

So, obviously, one of the most important phases of meiosis is the one that makes sure that the chromosome pairs head in opposite directions. In sperm, this isn’t a huge issue, there’s a process and everything usually follows protocol. The problem for women is that in human eggs, meiosis is not actually fully completed until the egg becomes fertilised. Right up until they meet a sperm, fall in love and get to baby-making business, eggs are stuck halfway through the meiosis process. A woman’s eggs effectively spend their lives suspended in action. Poised, but not ready.

To make sure that when the time comes to finish meiosis the right chromosomes run to the right end of the cell, the egg stores its chromosomes in tetrads: two chromosome stuck together. It’s basically a buddy system for DNA. The chromosomes are stuck together using a protein molecule called cohesin.  One of the potential problems with reproductive ageing is to do with cohesin. Research has shown that, in mice, cohesin doesn’t age well. Over time, it starts to fall apart and lose it’s ‘stickiness’. As a result, when meiosis is completed the chromosomes don’t always go exactly where they’re supposed to go, they’ve lost sight if their buddy, and now they’re the confused kid, running wherever the fancy takes them. If amongst this confusion you end up with an egg with too many, or not enough, or mixed up chromosomes, this can lead to infertility. The egg just isn’t okay for use. This is more likely to happen to eggs as you get older, so the chances of your fertilised egg resulting in a baby get less and less. 

This, to my knowledge, is the latest science on how women’s reproductive capabilities change with age. It isn’t proven to happen in humans, but it is proven that fertility declines in women as they age, so understanding this as one of the ways in which it might happen is both fascinating, and hopefully informative. Ultimately, the more we can talk about reproductive science, the more we will all know and understand our bodies, and the better equipped we’ll be to decide what to do with them. 

Categories: Becoming a Mother, Health
19 interesting thoughts on this


  1. Posted October 30, 2013 at 1:11 pm | Permalink

    I know we’ve had a discussion before about how awesome the AOW school would be. But this post has prompted me to say it again. I desperately want KL in charge of the science curriculum. How about a new AOW school post series?

    • Posted October 30, 2013 at 1:17 pm | Permalink

      If anyone fancies picking this idea up and running with it, I’d very much appreciate a Maths/Economics post on ‘how to know if you’re on the right tax code’.

      • Yanthé
        Posted October 30, 2013 at 2:07 pm | Permalink

        I had this very conversation with a friend last night Amy. She has just had an offer accepted on a flat and was distraught that we weren’t taught in school How To Be A Grown Up i.e. how to vote, how to buy a property, how to understand your wage slip!

        • Katielase
          Posted October 30, 2013 at 2:27 pm | Permalink

          I would also VERY much like a post on how my tax code is calculated, and what it means. And how they work out whether you get a mortgage and your repayment rates. I spent SO long trying to get my brain around this last year!

          KL x

      • deltafoxtrotcharlie
        Posted October 30, 2013 at 2:42 pm | Permalink

        Ugh, I concur


  2. Aisling
    Posted October 30, 2013 at 1:16 pm | Permalink

    The idea of my hyped-up, over-excited, enthusiastic but ultimately useless chromosomes running around like headless chickens made me cry. In a good way. In a, GOD THAT MAKES SO MUCH SENSE WHY AREN’T YOU IN CHARGE OF ALL SCIENCE EVER, way.

    Amy, that’s an insanely brilliant idea. AOW School term commencing shortly…

    • Posted October 30, 2013 at 1:21 pm | Permalink


  3. Hannah
    Posted October 30, 2013 at 1:42 pm | Permalink

    Kateilase, you are fabulous! The only things is, now I want to know more – I might already be a grown up, but can I go to AOW school too?

    My family has chromosome issues, this we discovered when my cousin gave birth to a very disabled little girl. It seems that some of my cousin’s chromosomes were matched up with the wrong buddy. This was also the case for my mum, aunt and nan but because all the chromosomes were there, just in the wrong order, it didn’t cause a problem. Unfortunately for my cousin’s little girl, her chromosomes didn’t copy perfectly (too many of some, not enough of others) and she ended up with very serious health and developmental problems. By a miracle of nature, neither me nor my sister have the mismatched chromosome problem but my mum did have many miscarriages along the way which we can only now understand why.

    I was only 18 when we discovered our genetic problem but I was adamant that I wanted a bloodtest to find out whether I was affected. The very lovely nurse sent to test me didn’t want me to be upset if I found out at such a young age that I was likely to have fertility problems. I agree that knowledge is power and I didn’t want to wait til I was 30 (thinking I’d be ready to have kids by then, pfft!) and then find out that conceiving was going to be more problematic than usual. Now I’m over 30 and still far from procreating, I wish there was an easy way to find out if I might have any other underlying problems. I’ve heard that there are certain tests you can have done (privately?) that tell you how far away from menopause you are / risk of early menopause, anyone know anything about that?

    Thanks again for these brilliant posts, making science accessible for all is a real gift!

    H xx

    • AJS
      Posted October 30, 2013 at 2:05 pm | Permalink

      Hi Hannah,
      Sorry to read of your chromosome issues, that must have been difficult to get your head around at 18. You mention a test for menopause; having jumped through all the hoops of infertility tests and then on to IVF, I do know that one of the tests they do (I had mine done on the NHS, it’s a blood test) is your AMH level (Anti-Mullerian hormone) which effectively measures your ovarian egg reserve and gives a good indication of how many eggs you’ve got left and therefore how fertile you are. There are plenty of charts online that show what the optimal range should be for your age.
      Hope that helps x

  4. Leni
    Posted October 30, 2013 at 1:52 pm | Permalink

    Fascinating KL – and so well explained! I will be stealing the sports hall analogy ( and possibly doing large scale student model with actual confused kids) to explain meiosis if that’s ok with you?

    I agree with the above posts. You could be the head of the AOW Free school? Or we could campaign to have you replace Michael Gove (making all teachers very very happy)!

    • Katielase
      Posted October 30, 2013 at 4:33 pm | Permalink

      I very much love the idea of kids actually running around a school hall to learn about meiosis!

      Pretty sure I’d be wildly incompetent at Gove’s job… but that said I couldn’t be much worse at it. And I have at least some common sense ;-p

      KL x

  5. Posted October 30, 2013 at 2:01 pm | Permalink

    Wow. Science just made a bit of sense. I love it when that happens.

  6. Fran M
    Posted October 30, 2013 at 2:25 pm | Permalink

    This is great – and actually makes sense!

    KL, have you read Expecting Better, by Prof Emily Oster? I’m currently reading it and it’s great. It’s not about the science behind babymaking, but has the same ideology behind it: that women should have the information at their disposal to make informed decisions about procreating. Totally think you should do the babymaking version of this.

    • Fran M
      Posted October 30, 2013 at 3:56 pm | Permalink

      Aha just had a chance to catch up on the comments from this morning’s piece… I can understand the criticism it’s received as it’s a personal interpretation of data – but an interesting read all the same :)

  7. another Sarah
    Posted October 30, 2013 at 10:07 pm | Permalink

    Thanks for sharing your knowledge Katielase. I discovered a national competition/campaign for educating and inspiring the general public about STEM subjects the other day. You should totally enter: Google ‘FameLab’!

  8. Posted October 31, 2013 at 9:39 am | Permalink

    This is brilliant! Explained so clearly and concisely, very powerful. And I totally want to enroll in AOW school please…. xx

  9. Rach M
    Posted November 7, 2013 at 8:00 am | Permalink

    Katielase, you are all kinds of awesome. This is brilliant. Xx

  10. AOWFan
    Posted November 26, 2013 at 5:42 pm | Permalink

    I did dissertation research on reproductive medicine (but am not a scientist) and this is still the first piece I’ve read that explains, very clearly and succinctly, to non-scientists/physicians, what the threat of “advanced maternal age” really means, AND finally makes clear why Down Syndrome is more common with maternal age. SO well said. Please write more!

    New York, USA

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