Predicting birth outcomes

I am not sure what to make to Steve Levitt's post today about ignoring medical advice on IVF implanting (ignoring advice still seems risky) but the last bit was amusing:

My favorite story concerns my son Nicholas:

Relatively early on in the pregnancy we had an ultrasound. The technician said that although it was very early, he thought he could predict whether it would be a boy or a girl, if we wanted to know. We said, “Yes, absolutely we want to know.” He told us he thought it would be a boy, although he couldn’t be certain.

“How sure are you?” I asked

“I’m about 50-50,” he replied.