Take one by mouth and call me in nine months:

Oral sex makes pregnancies safer and more successful – study: “New research suggests oral sex may not only help a woman conceive but may make her pregnancy safer and more successful.

The Australian study found that semen contains a growth factor which helps persuade a mother’s immune system to accept sperm.

It claims to have found evidence that regular exposure before pregnancy, especially by mouth, helps her immune system get used to her partner’s sperm.” Ananova