I have seen the claim that some sexual positions are better for getting pregnant than others. For example this article on how to have baby-making sex claims:
Be a missionary
It might seem like the boring way to get intimate, but the missionary position, with all that deep penetration close to your cervix, is going to give your partner’s sperm a little extra help in their swim for the egg!
Doing it doggy-style is guaranteed to get your partner’s sperm close to that all-important baby-making organ – the cervix.
Do these sexual positions increase the probability of conceiving?