Medications that block gastric acid secretion (called H2-receptor antagonists), such as Tagamet, Zantac, and Pepcid, seem to be safe to take while pregnant and fall into the “green light” category. However, even these medications should not be taken without a doctor’s advice. Over-the-counter antacids, such as Tums, Mylecon, Milk of Magnesia, and Maalox are all safe to take during pregnancy and are also in the “green light” category. Because it contains aspirin, Alka seltzer is not safe to take during pregnancy, although Alka Seltzer brand compounds that do not contain aspirin are safe. Phenobarbital-containing anti-spasmodics (e.g., Donnatal) are in the “red light” category since phenobarbital has been reported to harm fetal development.