Predicting Genders In Human Babies

[Silverbackman]

Though boys have a 0.2% higher birth, it is basicly 50/50. However is there a way to predict the gender of the baby based on how many kids you have?

Let us say you have 4 children, your first two kids are boys, is their a higher chance the next two kids you have will be girls (or at least one of them)? Or is always random no matter how many babies you have? Also if you have 4 children what are the chances all the babies will be one gender?

[mith]

They are mutually exclusive events. Just because you lose 500000 times at the lottery doesn't mean you're "due" to win. Same thing with flipping a coin, the coin doesn't memorize its position and determines which side to land on.

[victor]

Hey, I think I've read this.
"predicting genders of baby is depending on the vagina's pH when the sperm is trying to get in...if it's acidic then it might be female but if it's alcalic then it might be male.
I wonder what makes the vagina's pH become alcalic because as far as I know that there're flora microbia that maintain vagina's pH at 3.5...

[Chris4]

Doesn't this go completely against the fact that it all depends on the male. Whether the sperm contains an X or a Y chromosome?

[victor]

That's what I read in the general reproduction book...I don't know whether it's true or not...

[Chris4]

We are talking about humans here?

If the sperm has a Y chromosome then the baby will be male. Regardless of pH. The pH may affect how successful fertilisation is but it will be a boy. I have never heard of anyone checking pH.
That would also mean that if a woman had an unusual pH then she would always have boys or girls. Which isn't the case.

Can anyone else settle this issue about pH?

Also back to the first post. Boys have a 0.2% higher birth? I'm sure i heard more females were being born nowadays?

[MrMistery]

Of course it does not matter what the pH is at conception. Only if a higher pH somehow favorises a gamet containing the Y chromosome to fertilise the egg. But i simply can not imagine how that can happen.
About the actual question. This is really a mathematical question rather than a biology one: and the answer(and this will come as a shock to probably everybody on the forum)is: YES. But only in theory.
If you have a lot of babies(exceding reality)- about 200 or more you will see that the percentage of them is somewhere close to 50-50%. This is the consequence of what is called "The rule of big numbers" and it is advanced maths. I will not explain it now because the explination exceds my knowledge of maths.
But here is an example. More of an experiment. Take a coin just like mithril said. Heads or tails, mutually exclusive events. The maths principle known as the returned ball theory. Toss the coin once. It will land either heads or tails. Toss it twice. Same result. Toss it 5000 times and you will see that the result is close to the theoretical probability. Toss it 10000 times and it is even closer. The more you toss it, the closer to the probability it gets. Mathematical analaysis(I have been told ) is said to be able to demonstrate that if the number of tosses aproaches infinity the results aproach 50-50%. What do you learn out of this: no matter how lucky you are, if you play often at the casino, you will still lose becuase the laws of the universe are not on your side. If you win, stop playing

Totally off-topic, but good to know, ey?

[Chris4]

Doesn't the heads side of a coin weigh more so its is more likely to land on heads

[MrMistery]

That is cinical...

[Chris4]

I assume you mean cynical.

[MrMistery]

Yes i do. Sorry, it is 1 am here

[mith]

Who said it was an american coin? There could be some coins that are perfectly symmetrical...plus I know a couple of people who could control the force so well that it would always land on one side.