Why is Noah slightly deformed - The Grapes of Wrath?

Quoting the book:

"Pa thought he knew why Noah was strange, but Pa was ashamed, and never told. For on the night when Noah was born, Pa, frightened at the spreading thighs, alone in the house, and horrified at the screaming wretch his wife had become, went mad with apprehension. Using his hands, his strong fingers for forceps, he had pulled and twisted the baby. The midwife, arriving late, had found the baby's head pulled out of shape, its neck stretched, its body warped; and she had pushed the head back and molded the body with her hands. But Pa always remembered, and was ashamed."

Pretty much, Pa pulled the baby out, and misshaped it.