Diseases which affect gender ratio of births

October 8, 2007 5:12 AM

Hepatitis B causes mothers to give birth to fewer girls. Are there are any other diseases that affect births in a gender-specific way?
posted by Burger-Eating Invasion Monkey to Science & Nature (9 answers total)

Toxoplasmosis is suspected of having such effects, see note 3 below the wikipedia article.

On a side note: There was an article recently that claimed "beautiful people" (whatever that means) tend to have more baby girls, it was explained that "beauty" genes tend to work better in girls, so as a side effect the same genes tend to cause female babies. I cannot find that article right now.

Personally I don't believe any of this has significant effects. The ratio between boys and girls has always been about 51:49, and from what I've read that didn't change much in the last 100 years. Often the numbers don't add up: I read an article claiming that 40%(?) of all women in industrial countries are infected by toxoplasmosis and that this infection causes a shift in the girl/boy ratio to 60:40. The problem is, this change in ratio doesn't manifest itself (in this case 54:46)

"Boy or girl" seems to be such an important question to many people that they'll swallow any "scientific news" claiming to have found a significant effect in one way or the other. Just google it, you'll find 100 theories either explaining why we are seeing "more girls" or "more boys".
posted by Nightwind at 5:40 AM on October 8, 2007

I think I had read something about Toxoplasma gondii doing something similar, read up on it.
posted by PowerCat at 5:40 AM on October 8, 2007

Not a disease exactly, but some chemical pollutants are being blamed for some changes in sex ratios. Article here.
posted by DarkForest at 5:44 AM on October 8, 2007

Wikipedia also has something on this.
posted by DarkForest at 5:48 AM on October 8, 2007

Not a disease which affects humans, but the bacteria Wolbachia lives in the cells of invertebrates, and can only be passed on through eggs in females and not the sperm of males. They have a number of strategies, including ensuring that uninfected females cannot reproduce, killing any male eggs they infect, and feminizing the infected males. Thus, populations infected with Wolbachia tend to have sex ratios skewed in favour of females. Fortunately, they don't infect vertebrates.
posted by penguinliz at 7:54 AM on October 8, 2007

A salon article from today mentions declining male births possible related to testicular cancer.
posted by xorry at 8:18 AM on October 8, 2007

Fathers who are exposed to conditions which tend to mutate/damage sperm (e.g. deep sea divers, military air craft pilots) predominately father daughters. Fathers who have non-Hodgkins lymphoma are far more likely to have daughters (154 out of 190 in one study).
posted by Wavelet at 9:00 AM on October 8, 2007

Lupus may tend to bias births toward males:

To explore the causes of complications in pregnant women with systemic lupus erythematosus (SLE), we prospectively evaluated 34 pregnancies in 28 SLE patients, and 2 additional pregnancies in patients with lupus anticoagulant and positive antinuclear antibody, but no other manifestations of SLE...

Twenty of 29 (68%) children were identified as male...

This seems particularly interesting to me considering the especially long shadow lupus casts into the normal population.
posted by jamjam at 9:06 AM on October 8, 2007

Not a disease, but you may be interested in the Trivers-Willard hypothesis.
posted by scodger at 11:52 AM on October 8, 2007