Here's an interesting factoid I recently learned in a child dev class:
Women/girls who are impregnated by teenage boys have boy babies about 86% of the time.
That is because, until a male reaches complete physical maturity (often as late as age 17-18), he typically does not produce viable X-sperm (girl-sperm), although he may have plenty of Y-sperm (boy-sperm).
Interesting idea, and now that I think about it, both of my kids (conceived while my ex and I were teens) were boys, and most of the other very young couples I knew also had boys.
I'm wondering if any research has been done on the opposite end of the spectrum: do old men tend to produce more girl-babies? Do their Y-sperm die out at some point, leaving only X-sperm?
I hope so, because my husband's 40 years old, and I want a girl!!