I’m in the middle of a discussion with a coworker about the gender of newborns. It’s pretty well known that the father determines the sex of the child, depending on whether the sperm is carrying an X or Y chromosome. The question is - is there such a thing as the sperm being dominant in one chromosome or the other?
I’m inclined to think so - since my sister has four boys and my sister’s husband’s family has always given birth to males. Also, another coworker of mine just found out that his to-be newborn is a boy, and his family has also given birth to all males.
Does anyone know of a credible reference to support either side of the story?
In terms of numbers, X and Y sperm are exactly even in distribution. However, there are subtle differences in the way each type moves, leading to some interestingtechniques for attempting to select the sex of your baby.
Additional studies have shown that babies that are concieved through IVF are more often males than females due to the faster swimming of fresh samples when injected IC and the fact that for some reason the male sperm seem to survive the freezing process better for frozen samples.
There’s also the possibility that certain women, due to their “vaginal environment”, are more prone to conceive one sex or the other.
Acidic = girls and
Alkaline = boys.
I can’t find a cite that flat out states this as fact, but many of them call it a ‘possibility’ or a ‘tendancy’, so take it as you will.
I’ve even heard claims that douching with certain compounds right before sex can be a type of poor man’s sex selector.
I’m not sure if you were referring to me or Belladonna so I will share some information.
In his book “How to choose the sex of your baby” Dr Landrum B Shettles covers various reports from research that he had done with indicated that the Y sperm are lighter, swim faster but die sooner and X are heaver Swim slower and live longer. In this book he also states that due to the makeup of the sperm the timing of intercourse weight heavily on conception due to the PH levels of the cervical mucus pre and post ovulation.
Also in these studies he states that due to the weaker nature of the Y sperm, better timing is needed to have a girl, because the less hearty Y sperm will die off prior to the meeting of the egg and there will be a higher count of the X sperm.
Due to the weaker nature of the Y sperm, they are also less likely to survive the freezing and thawing process used with non-fresh sperm donors, thus the higher rate of boys in patiens using DI, IVF and ICSI.
Another side effect of this is if the mother’s PH levels are particularily harsh it may make it near impossible for a girl to be concieved at all.
I’m sorry I was misreading some information permit me to correct.
Actually the freezing process is less of a factor in DI than the timing of the cycles and the mucous quality. I had made a false assumption, and as i read on in the article i realized I had to correct myself.
In cases of DI most patients use a Basal temperature monitoring system that indicates when ovulation should occur. When insemination occurs during the ideal Basal stage, the cervical mucous and acidity is prime for the Y sperm to swim more quickly and reach the egg first. It turns out in cases where insemination happens at multiple timeframes (pre and post ovulation) the number of boys and girls is mixed.
However, in the case of couples having standard sex, timing and the PH level of the woman’s crvical mucous would be the largest detemining factors. In the cases of female family members all having boys, or male family members all having boys, the results are most likely based on either the resiliancey opf the sprem for their genetic type, or the PH level of the women.
Still, it’s odd. I have 3 brothers, to one female me. My brother has 4 daughters. As far as I know, all my male cousins on my father’s side have sired nothing but girls.
I have 4 girls. My brother-in-law (husband’s brother) has 2 boys. It’s something just…odd. I knew a family once that had 7 girls in a row. Never did have a boy. Finally, their oldest (teenaged) daughter had a baby boy out of wedlock, and he was being raised as the ‘youngest child’, since his youngest aunt was only 4 at the time.
It’s just strange to me how that kind of single-sex family can happen.
You know, I’d be really interested to know just how often it does happen. I come from one myself–I have five sisters and no brothers. I’m the only one with kids so far, but I’ve had two sons.
I’ve got a various cousins and aunts with anywhere from two to five daughters only, and one cousin who had five sons and only one daughter. It seems so unprobable, that there almost must be influencing factors involved. Does anyone remember enough high school math to figure out the probablility of four, five, or even six daughters in a row?
I once looked into this sort of thing using a big database of human pedigrees. I was interested in segregation distorters, genetic elements that spread themselves by biasing transmission in their own favor. A segregation distorter located on the X or Y chromosome, and acting in males, would bias the gender of the offspring of a carrier male.
I found that the distribution of the numbers of boys and girls in a family looked close to what you would expect if all males (in fact all couples) produced the same sex ratio among their children. For example, the distribution of the number of girls in a family with eight children was about the same as the distribution of the number of heads occurring in eight fair coin tosses (a bit different because the fraction of males is a bit over 50%). This can’t rule out the possibility that there are rare fathers that are highly biased, but it seems to say it’s not the general phenomenon that various anecdotes might suggest.
Don’t think so. That’s the probability to have six boys, but the probability of having six children of the same sex would be 1/2[sup]5[/sup] == 1/32 == 0.003125.
In the same way, the probablity of having two children of the same sex, is the same as having two children of different sex. The odds of having three children of the same sex is 1/4. Not all that unlikelly.
(All this assuming that the M/F odds are the same. Personally I think that most of the variations can be ascribed to statistical fluctuations, although it would indeed be interresting if there was more to it.)
