Why can't I conceive a boy?

05 July 2016


I have 5 girls. For 15 years, I have wanted to have a boy - I changed my diet, used ovlution kits, etc but they did not work. Could you please try to explain to me why I could not conceive a boy????


Kat Arney put this to fellow Naked Scientist Chris Smith...

Chris - Well, it's actually her husband's job, isn't it? Because as geneticists will tell you, there are sperms that have X and there are sperms that have Y. if you are having a girl then your egg is being fertilised by a sperm that has an X chromosome in it. if you are having a boy then your egg is being fertilised by a sperm that's got a Y chromosome in it.

Kat - Because women's eggs just have one X chromosome. All eggs have an X chromosome.

Chris - That's right. Women are just XX. That's their genetic makeup whereas men are XY. Therefore, the only genetic material a woman can contribute to her egg is an X chromosome whereas men can make sperm that have either an X or a Y. Now, why should you only have girls? Well, what's the chance or having a girl? You've got roughly a 50/50 chance because there's equal numbers roughly of X and Y sperm in a healthy person. So, what's the chance of having five in a row? Well, that's 1/2, a half to the power of 5. So that's a half times a half, times a half, times a half. and that means you've got one in two times one and two is one in four, times one in eight times two again, one and 16, times two again, one in 32. It's about a 3 per cent chance. That's happening. But that's not zero. And so therefore, just because it's low odds doesn't mean it is abnormal. So I would say that somebody has to be that 3 per cent because we believe that the population is what we call a normal distribution. So it's probably perfectly natural. There's probably nothing that this lady can do to shift the odds apart from - to go and see a clinic who can put the sperm through a system to sort out the X and the Ys which you can do. Some people don't agree with it. they don't think it's ethical. It may also have health problems. Who knows what the long term consequence of doing this is and thwarting nature in that way. But the bottom line is, you should be as one person - put it to us - delighted you've got five girls because they're much easier to bring up than the male equivalent. Because they said the conversation extends beyond 'yeah' unless of course you happen to like all the mates around from the pub for beery parties and shirts and stuff strewn all over the dining room.

Kat - I think girls smell nicer as well.

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