What Happened at the end?

I will be honest, I don't remember this whole film but....

I remember the very end because it was creepy..... Dr. Hatch captures the preganant woman and takes her back to his doctor's office, where gives her an epidural to make her completely numb and immobile from the waist down (she's still unconscious, I think he had drugged her not sure).
But then she wakes up and realizes what is happening. Dr. Hatch is preparing to perform an abortion on her. She cries and begs for him not to do it. He says Don't worry you won't feel any pain. I made sure.
He turns his back to her, and she sees another syringe laying near her. She slips it inder her sheet.
She calls Dr. Hatch over and smiles at him and says his name lovingly, pretending to be his mother. And says it again. He smiles and leans over and says "Yes?"
She whips out the syringe and stabs him in the neck. He looks horrified, and dies. She lays there, half-sobbing. Off screen she is brought home.

Hope this was helpful!

It was really pittiful in a ways, before he dies he has a flashback of his mother. Sort of messed up, but sad. (after as said above being stabbed). She was his mom (the woman who resembled) and he had some kind of infatuation with her, (Norman Bates style), it wasn't confirmed though about his brother, but you can tell from all the clues because the "baby" took his mom away.

I thought earlier in the movie, Aunt Sylvia confirmed that the baby brother was killed so Myron could have his mother to himself.

Life is never fair, and perhaps it is a good thing for most of us that it is not.

She looked like his mom
He killed his baby brother