There's a report on ABC (link no longer available; original article was previously posted at http://www.abc.net.au/news/newsitems/200505/s1374229.htm) about a paper in the Journal of Theoretical Biology which states that people in professions such as engineering and accounting have significantly more boys than people in professions such as nursing or teaching.
According to the report, engineers and those in similar professions ("systemisers") have about 140 boys for every 100 girls, while nurses and those in other "caring" professions have 135 girls for every 100 boys.
Hope you weren't counting on a bunch of daughters!