With the Whelan Method, you are to have sex four to six days before your temperature rises if you would like to have a baby boy. If you would prefer a girl, wait until two to three days before ovulation to have sex. Whelan based this on a study of 1,300 women charting their temperatures done by Dr. Rodrigo Guerrero.
According to this method and the book giving more details, Boy or Girl?, the success rate for having a girl is 57%. There is a slightly higher success rate for having a baby boy with 65% of the time people conceiving a boy. This method is in direct opposition to the Shettles Method. In fact, there are several pages in Dr. Shettles' book talking about the Whelan Method.
Sources:
Type and time of insemination within the menstrual cycle and the human sex ratio at birth. Guerrero R. Stud Fam Plann. 1975 Oct;6(10):367-71.
Boy or Girl? Whelan, E. Pocket, 1991.
