This is quite interesting.

[pie]

I wanted to post this in 'In the News' but it seems to be down.

I have had on m/c after a girl, does anyone want to talk about whether this has been true for them?

Maybe some hope for the future though.

I saw this too Pie. My pregnancy loss was after a healthy boy, so I was very interested in this story. I have been told that from conception onwards baby girls are more robust than boys, less like to miscarry/be stillborn etc, and that was one of the reasons we decided to try and find out the sex of the baby I am now expecting (a girl).
I know two other mums who lost babies after their first, boy, babies.
Part of me feels that this may need further investigation before it can be conclusively proven, but it's an interesting study and I certainly wish there was a lot more done on possible links to miscarriage and pregnancy loss.

Aren't all foetuses the same sex, ie female, for the first few weeks and then something triggers a hormonal switch to turn them into boys?

Don't know how many weeks, and the report doesn't say at what stages of pregnancy the miscarriages it refers to have occurred, but I wonder if in some women it might work like the Rhesus factor - the first boy sets off antibodies to male hormones?

This is interesting but, off the top of my head, I can think of 3 people who had miscarriages after having a child (seem to be more before having a child at all). 2 had already had boys an one had had a girl. All went on to have boys so...bit inconclusive. But it would be very satisfying if they could eliminate some cause of miscarriage

I saw the same story reported in The Guardian . It is interesting, although I wonder if the number of women studied was enough to make the statistics reliable? FWIW, I have had 2 very early miscarriages following a boy.

There is some evidence that the more elder brothers a man has, the more likely he is to be gay. This was also explained by the immune response theory, in this case altering the hormone balance in the womb. Interesting, i thought.

Really? Do you have a link, aloha?

Janh that's interesting but although the "blueprint" is female, I don't think it works quite that way. Boys are XY and girls are XX so both contain X (the blueprint) but these are determined at conception.

A very interesting theory ... I had a boy before I miscarried ... hmmmm ....
Not what I need to know at the moment though as I am coming up to 10 weeks and still can't help worrying ... so I won't enter into this thread too much ladies ... if you don't mind!!!

I think what janh is thinking of is that the immature gonads, whether ovary or testis, look identical to start with and then after a hormonal switch the testis starts to develop differently. But you're absolutely right, it's the chromosomal constitution that determines sex (aside from rare mutations), and that is determined at the moment of conception depending on whether the successful sperm is X or Y bearing.

I had a miscarriage after having DS.......mmmmmmmmm.

I think up until about 6 weeks all fetuses LOOK female, but then at 6 weeks the presence of the Y chromosone start the male development process. As the fetus has already begun developing LOOKING like a girl the nipples stay.

I read this:

You're both right-sort of. Yes, sex is determined genetically at conception
by the inheritance of either two X chromosomes (female) or an X and a Y
(male). The expression of the sex characteristics doesn't begin until about
6 weeks gestation. Before that time the fetus is not really male or female,
but non-specific. The fetus has two non-specific gonads and two sets of
tubes. If the fetus has a Y chromosome, at 6 weeks a gene called the SRY
(sex determining region of the Y) turns on. This gene causes the
degeneration of the female characters and causes the male characters to
develop. It causes the non-specific gonads to become testes and the tubes to
become the vas deferens. Once the testes are mature enough another gene
turns on to start producing testosterone. This causes the internal sex
organs to develop. Part of the testosterone turns into another hormone which
then causes the external sex organs to develop. If the Y chromosome isn't
present the female pattern of development occurs; the female pattern is the
default pattern so-to-speak. The gonads become ovaries and the tubes become
fallopian tubes. So even though the gene for maleness is inherited at
conception, the expression of the trait doesn't begin until about 6 weeks.

In a molecular biology book.

Didn't cut and paste that right, its from an e book left over from an ethics course, don't know why I even have it!!

But I think it gets the idea accross.

Ghosty - if you're still reading this thread - think of all the families you know that have more than one child, with the firstborn being a boy! Statistics are just statistics after all - and they may be incorrect.

What I mean is, what may have been found in this study might not be true for the general population (trying to reassure myself here too...)

Hewlettsdaughter, look it up at www.uk.gay.com/headlines/4046. There is theory that this is caused by the women producing antigens to the boy foetus's Y chromosome (which we do) which leads to an increase in homosexuality. As homosexuality is not that common the absolute percentage is still pretty small - up from 3per cent of first born boys being gay to around 5per cent of third boys being gay. As a percentage rise this is still quite large.
I suspect both studies are quite correct but of course an increase in the chance of miscarriage is not at all the same thing a probability.

Cheers aloha, I'd never heard of that before.

While I do think statistics can be very important (I work in a medical statistics department!) I have also learned that some statistics need to be taken with a pinch of salt. That's not to say I don't believe either of these studies. But you do have to be careful, make sure that studies are done rigorously, with enough numbers to make the statistics reliable.

The brother study is part of several studies involving 7000 men and has been replicated and published in New Scientist and Nature. I think both of these studies have been peer reviewed and are considered sound and the numbers in them statistically significant.

Thanks, pie (and CAM and tamum), it occurred to me later that they can sex embryos before IVF implantation so I'd got something wrong - it was the nipples thing I was thinking of.

Ghosty, dear, don't panic, they're not talking about the general population - just that some women might have this tendency - a small minority, like the R negative ones. And aren't they saying it can be fixed now they've found it? (must go and read the pieces again!)

Aloha - fair enough. I wasn't particularly singling out either of the studies mentioned here, just trying to make the more general point that it's good to get the context - so thanks for your reply.
One thing I worry about is how the media picks up on studies and twists things, either by reporting a statistic incorrectly, or concentrating too much on one statistic and ignoring the rest.
Those of you interested in checking out the facts behind some of the bigger health stories should look at the Hitting the Headlines section of the National electronic Library for Health website. I find this quite useful.

I actually agree with you. When I write about health I always try to go back to the original study rather than relying on reports of it, as they are often inaccurate. But the little brother hypothesis is good research I think.