I have read that it is just a myth. There is no proven study that confirms that positions increases the chances of getting pregnant. However, during intercourse the semen does tend to come out more when woman is upright in a sitting position or standing. If you are planning on getting pregnant, I can recommend a book by Dr. Olson. She gives you tips and techniques on how to get pregnant faster naturally and holistically without drugs and treatments. I reference the book here waystohelpgetpregnant.com/