There is no proof doing this will improve your chances of getting pregnant.
Theoretically, this may seem like a good idea. By lifting your legs, your pelvis is elevated, therefore allowing the sperm to find the egg quicker. But all this will do is make your legs numb.
There is no harm in slightly raising your pelvis by placing a pillow under your hips, you do not need to lift any other body parts in the air. Likewise, doing handstands is not necessary.