You cannot do anything in your sexual habits to change the sex of your baby. All men who produce viable sperm produce both male and female sperm, and both have an equal chance of fertilizing the woman's egg. Through in-vitro, however, a doctor could take a female zygote and implant it into your womb. Followup There is a technique called "sperm spinning" which can influence the gender of a baby before conception. Most methods of trying to influence baby gender need to happen before conception. There are other methods that claim good results (70%+) as well, but they are often trade secrets.