Click here for the whole article.
In the population as a whole in Britain, roughly 105 boys are currently born for every 100 girls, according to the study, The Sunday Times newspaper said.
But according to calculations by chief researcher Satoshi Kanazawa, for engineers and other "systemisers" [a description given to a form of cognition considered more "male"] the ratio is 140 boys per 100 girls.
Nurses and the like produce around 135 girls for every 100 boys, the study found.
Although not addressed by Truck and Barter, I think there's another possible reason for the linkage between parental job and offspring's sex. If higher-testosterone individuals are attracted to these professions, and these same individuals are more likely to have male children, you could see a relationship between parents' careers and the sex of their offspring that has little to do with the actual career.
I'm assuming that the sample is a cross-sectional one. So, there could be a spurious correlation effect. Of course, if it's the job that's driving the sex of the child, you could test it by looking at children in parents who had one child while in a "feminine" job and one while in a "masculine" job. This way, you've controlled for the non-job characteristics, and are splitting out the effect of the parent's job on the offspring's sex.
Update: here's a link to the article, courtesy of JoanneJacobs.com