Smoking while pregnant?

My wife used to be heavily involved with drugs (crack, heroin and pills) she went to rehab for this problem about 2 years ago and she's been clean since, or so I've been told. After her rehab we decided to put the past behind us and decided to have a child. She is now 4 months pregnant and I recently caught her smoking crack again. I am VERY concerned. I know drugs can harm a child and give birth defects as well as mental defects. Im assuming my wife has been smoking the whole 4 months, with all the crack smoke probably affecting the baby, what are the chances it will be born black?