Actually, gentlemen, not such a dumb question as it may appear!
The sex of the foetus is, to a degree, determined by the level of several hormones in the father's sperm at the time of conception. When the father is under stress, the hormones are programmed to favour the procreation of a female foetus. This goes back for millions of years. It is essential that nature provides a surplus of females to ensure survival of the human race. One male can impregnate thousands of females if necessary, lucky us. So if you're under stress, or off to war, or both, you have more chance of fathering a daughter. This was what was found in a survey of fast-jet jocks several years ago. Exposure to radiation is another ongoing survey among the pilot fraternity. I was a pilot for 40 years and fathered one of each. So back to the drawing board!