In a study published July 12, 2011, British researchers revealed that smoking during pregnancy increases by at least 25% the risk of birth defects such as missing or deformed limbs, clubfoot, skull defects and cleft palate, with a 50% increased risk of the child being born with a condition where the intestines protrudethrough the skin.

http://medicalxpress.com/news/2011-07-deformed-limbs-linked-pregnancy.html
http://www.sciencedaily.com/releases/2011/07/110711195019.htm
http://www.ucl.ac.uk/news/news-articles/1107/1102201101-birth-defects-smoking-pregnancy