The traditional version of this medicine was made up of citric acid, sodium bicarbonate (which makes the fizz), and aspirin. But this drug has changed since your grandpa took it after a long night of fun.
Alka-Seltzer offers a wide variety of products now, and each one has slightly different ingredients. Aspirin is considered safe during pregnancy in low doses (60-150 milligrams daily), but the Food and Drug Administration (FDA) reports sodium bicarbonate may cause harm to developing babies.
Studies on sodium bicarbonate are out of date, though, so your best bet on this one is to give your provider a quick call and ask. They’ll be familiar with the ingredients on the list and be able to guide you toward the safest option.