25% Chance, Egg that grows into a large snake.
25% Chance, Egg that is a lamia.
25% Chance, Live Birth Human with snake features. (Fangs, reptile eyes, scaly skin)
25% Chance, Live Birth Normal Human
I'd like to imagine getting a Lamia pregnant is a crapshoot about what you'll get. Which is part of the fun for you and for her.