For pregnancy to happen, sperm must get into the uterus and fertalize an egg. If you put the sperm in someone’s mouth, it could only get to the uterus if it then leaves the mouth and is somehow deposited into a vagina.
In theory, that could happen if the giver takes sperm into their mouth, then transfers it to someone’s vagina, which could happen if the person spits it there, or if there is direct contact between the mouth that just received sperm and the vagina.
Swallowed sperm will never reach the uterus. There is no internal connection from the digestive tract to the reproductive organs. But….
Recorded in the 1988 edition of the British Journal of Obstetrics and Gynecology, the incident occurred after the girl had been stabbed in the stomach by a former lover who caught her in the oral act with another man. Doctors at the hospital discovered that the wound opened up a hole her stomach near the rest of her abdominal cavity. They stitched both holes up and discharged her.
After 278 days, however, she returned to the hospital complaining of abdominal pain. Upon evaluating her, the doctors were surprised to discover two things: She had no vagina (merely a dimple instead), and she was carrying a full-term infant. A cesarean operation had to be performed to deliver the baby.
Since no vagina obviously means no traditional pregnancy, doctors concluded that the child had to have been formed by the sperm escaping from her stomach via stab wound and settling down in her reproductive area. Coupled with the absence of gastric acid during the initial operation, doctors believe that is what could have allowed this extraordinary pregnancy to occur.
Babies result from semen entering the vagina whilst the woman is ovulating and one sperm managed to reach and fertilise a released egg.
Now there are numerous ways that pregnancy can result from oral sex but they all involve sperm entering vagina and meeting egg.