He was fucking her.
As she lay flat on her back, he held her ankles and spread her legs as wide as possible. He liked it that way because it showed that he was fucking her, that his cock was going deep in her pussy.
You could say he was drilling her, hammering her, nailing her, plowing her, pounding her, screwing her, spearing her: All of those gerunds of aggression, if not violence, often used to describe sexual intercourse, especially when one partner wants to orgasm without concern for the sexual desires of his (usually) partner.
As he said, "Take it all, you hot little fuck. You know you want it..."
Three years later, he met his son...the one he had fathered that moment...the one he never knew he had...
So he must have plowed her, because he had planted a seed that had grown.