Science Questions

Why can't I conceive a boy?

Mon, 4th Jul 2016

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Safia asked:

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...Twins - Identical?

Chris - Well, itís actually her husbandís 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 thatís got a Y chromosome in it.

Kat - Because womenís eggs just have one X chromosome. All eggs have an X chromosome.

Chris - Thatís right. Women are just XX. Thatís 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? Youíve 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 thatís a half times a half, times a half, times a halfÖ and that means youíve 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. Itís about a 3 per cent chance. Thatís happening. But that's not zero. And so therefore, just because itís low odds doesnít 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 itís probably perfectly natural. There's probably nothing that this lady can do to shift the odds apart from Ė 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 donít agree with it. they donít think itís 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 Ė put it to us Ė delighted youíve got five girls because they're much easier to bring up than the male equivalent. Because they said the conversation extends beyond Ďyeahí 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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On a population-wide basis, every time you have a child, there is about a 50% chance that it will be a boy.
If you tried again, the chance would still be around 50%.
The odds of getting 5 girls in a row is 1:25=1:32, or about 3%.

Since there are many women having babies, somebody has to be in this 3%.

The really interesting question is if there is some factor that biases the sex ratio in your case.
My old boss used to say that electrical engineers have 2/3 girls, but I'm not sure how scientific that was.

One study suggested that women in high-stress jobs tended to have more daughters:

Another study found no significant relation to father's occupation:
evan_au, Fri, 17th Jun 2016

Congratulations on having 5 girls. Tim the Plumber, Fri, 17th Jun 2016

In order to conceive a boy child, you need....wait for it.....a male sperm.

If you have not conceived a boy, then you are not getting enough male sperm to do it. There are lab procedures to concentrate male sperm cells if you still want a boy.

You should think twice about that, at this time, I think.. I have known men who were raised with 5 older sisters. They grew up to despise women. eeyore, Fri, 1st Jul 2016

Exactly. The sex of a child is determined by the sperm, not the ovum. Ther's an old wives' saying that it takes a strong man to father a daughter, so you have obviously chosen your partner(s) well.

And believe me, girls are much less trouble to raise. Even if you long for the smell and the fighting and the dirty clothes and the insatiable appetite and the drunken friends and the bent cars and bits of'll appreciate a conversation that goes beyond "yeah." alancalverd, Fri, 1st Jul 2016

The sex of the live-born child can be affected by the prenatal environment ... RD, Fri, 1st Jul 2016

OK, let's be pedantic. The sex of a blastocyst is determined by the sperm, but its survival is determined by the placenta, and it may just be that women who consistenly bear children of one sex alternating with miscarriages, are indeed selecting the sex of their offspring.

The problem is that spontaneous abortion in very early pregnancy is so common that few women notice it, and you would need to have about a dozen healthy daughters for the bias to be statistically significant. That said, five on the trot, especially if they have different fathers (which is why I raised the possibility earlier) , does indeed raise a suspicion of placental bias.  alancalverd, Fri, 1st Jul 2016

Here is how the question of why a woman cannot conceive a boy is resolved among the Montagnards of Viet-Nam and Laos.

The man marries an additional wife. If she only conceives daughters, then the matter is settled.

That having been said, I believe the lady is asking for help in conceiving a boy. This is no place to get help. The lady's obstetrician is the proper venue. eeyore, Fri, 1st Jul 2016

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