It might not impregnate if most of the cum drips out. Missionary and legs high up after are your best friend. Or doggy style with the proper angle if you are long enough to hit the cervix and inject directly into the uterus.
I got a gal pregnant in that position. She was mad actually that I blew my load in her while she was standing since she wanted to get pregnant. Surprised both of us that it worked.
Delightful!!