Strollerderby

Girls Only: No Boys Born in Growing Number of Towns

Posted by Madeline Holler

Desperate to have a baby girl? Well you might think about relocating. Or eating more marine animals. 

Researchers have discovered several towns where women are only giving birth to girls. The gender balance is totally out of whack and something like a 2 to 1 ratio of boys to girls.

Where are these towns of rainbows and ponies and sparkles and all Hannah Montana all the time?

They are Arctic communities up in northern Greenland. What's causing this. Most likely, PCBs.

Here's an excerpt of an interview with concerned researchers on NPR's Living on Earth about the PCB-girl baby connection:

Now, looking at your report here I'm just struck by the apparent effects that PCBs have on the sex ratio of children and the way it changes ... The chart that you have there shows that as you increase exposure to PCBs, at first you get way more boy babies than girl babies. But then as you go higher and you get above four micrograms per liter of blood you get way more girl babies.

How could this happen? Here's what Lars Otto Reiersen, executive secretary for the Arctic Monitoring and Assessment Program, says: 

Well, it could be what we call the mimic of the hormones. That early in the pregnancy that some of these pesticides may mimic testosterone or estrogen. That's documented from science. So, that might be what's occurring but that's too early to say for sure what's the mechanism.

Well that's just kind of yuck. Plus, the girl babies with moms who have a higher concentration of PCBs in their blood have a lower birth weight and much earlier births. So it's not all tea parties and frilly socks and two girls for every boy; there are serious health consequences.

Still, here's what I don't get. I thought gender had more to do with Dad's sperm than mom. He's the one shooting Y chromosomes for boys and X chromosomes for girls. Are they studying sperm in all this? Or are these children actually hermaphrodites -- in this case technically boys with female characteristics? Or do I need to go back to sophomore biology?

Think it's no big deal for those of us who are not dining on PCB-rich walrus fat? Actually, everybody around the world has some level of PCB exposure, just different concentrations of it depending on where they live and at what level of the food chain they typically eat. The next question is, what has the impact of low exposure been? 

 

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Photo: bodis-wallner.com

 


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Comments

 

Tired Girl said:

I could be wrong, but I think there's a theory that even the the sperm decides the gender, the egg, the timing of intercourse, and the environment (temperature, acidity) in the uterus may give an advantage to one type of sperm (x-sperm or y-sperm) over the other. Something like, x-sperm live longer so if it's 36 hours before ovulation, then a girl-forming sperm gets the advantage (I don't know the specifics, though), but if it's 6 hours before, then the boy-forming sperm gets gets the advantage.

Crap, I don't think I've ever typed "sperm" that often before...

July 30, 2008 5:07 PM
 

Madeline Holler said:

Yeah, I thought of that too. The researcher's all "in the early stages of pregnancy, the hormone levels" blah, blah. And I'm thinking -- shouldn't we be, in line with what you're saying, Tired Girl, talking more about the time of conception at least?

Thanks for writing in with all that sperm!

July 30, 2008 5:15 PM
 

Chris. said:

I read also (who knows where?) that male fetuses are much more sensitive to adverse conditions early in the pregnancy and will often miscarry, before the mother knows she's pregnant.  So there could be just as many male pregnancies, but only the female ones are making it.

July 30, 2008 11:29 PM
 

steffmarcusky said:

Also, did they talk about how many of the girls are actually single X, instead of 2Xs? Supposedly, there are 1 in every 2000 births where the sperm doesn't give either an X or Y, therefore she's a she by default. Problem is, she's likely infertile and exhibits certain characteristics that I can't remember - it was in an earlier blog post on Strollerderby.

I agree with Chris. that it's probably that the male fetuses aren't making it.

July 31, 2008 8:31 AM

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