Well.... besides the fact that I don't think it would work, and it would probably just cause some sort of birth defect, since the sperm are what determine the baby's sex... Yes, I think that would be unethical. I think that that sort of thing is best left up to chance. It's not like you're trying to prevent a disease or something, you're just willing to risk the health and safety of yourself and your child in order to try to have a boy or girl.

That depends entirely on your own personal ethics, nobody can answer this question for you.

Only if it's unethical for her to get pregnant in the first place. Though in reality, it's likely to have side effects. It may cause deeper problems. Birth defects like Jennifer said, but no, it's quite possible, the sperm is not what determines the baby's sex, not directly at least. The sperm determines whether the baby gets XX or XY (assuming the MOTHER is all X and not an XY that was manipulated to being a girl by HER mother - in that case, the offspring would be a boy 2 thirds of the time, a girl one third - if the fertilized egg gets YY, that's non-viable, and she just wouldn't get pregnant), and THAT determines the enzymes that will be present in the embryo and THAT determines sex, so taking the enzymes directly CAN effect it by short circuiting the chain and not letting the DNA determine the enzymes present - it's one of the causes of hermaphroditism in humans for instance, so yes, it can backfire. If you weren't risking giving the offspring a deformity, then of course it wouldn't be unethical. The Chinese leaving their girl-babies in the Gobi desert to die because they're only allowed one child each and they all want boys. THAT'S unethical.