Alex was more than aware of the potency of his seed, and just how effective it could be in human women. Anna was different, so, he was particularly anxious to see just what kind of upgrade the elf leader would obtain from this encounter. Asides from that, he knew that she would try her best to maintain her distance after a memorable night like this. That was the mature thing to do.
But Alex grinned wickedly when he remembered just how addictive women could get to his semen. For their bodies, it was like a drug they simply could not have enough of. So, he was anxious to see just how well Anna would fight her instincts to stay away from him.