Combinations of CYP2A6*4 and Glutathione S-Transferases Gene Polymorphisms Modify the Association Between Maternal Secondhand Smoke Exposure During Pregnancy and Small-for-Gestational-Age … See original – Combinations of CYP2A6*4 and Glutathione S-Transferases Gene Polymorphisms Modify the Association Between Maternal Secondhand Smoke Exposure During Pregnancy and Small-for-Gestational-Age