Oh and definitely not a stupid question its just one of those fun gender games :) pass it to your pregnant friends sees what they say.
If you see a dark red V (also resembles Y or a W, not lines) shaped vein s at six o'clock on your left eye ball its a girl and on your right its a boy. I've noticed its about about 90% true. About 90% of the time that its wrong its usually saying your having a boy when you are actually having a girl. The other times its wrong is when it says your having a girl when you are having a boy, you just don't see any lines or its in both eyes but all this is super rare. The reason why I think it is possible to get a false reading is because all our bodies are different and handle pregnancies differently. Women however have actually watched it switch eyes with each pregnancy. Some say its do to the high levels of blood that circulates you're body while pregnant and the different hormones your body has from the certain gender. Its pretty cool.
it has something to do with looking at your eye lid and if you see the vein in one eye its a girl if it in the other its a boy. it's like the ring test and the calendar predictions.