The short answer: Tums (calcium carbonate) is widely regarded as a first-choice antacid for heartburn in pregnancy when taken at normal doses. Major bodies like ACOG and the NHS point to calcium-based antacids as an appropriate option for pregnancy heartburn. This page reflects that guidance, but it isn't a substitute for advice from your own provider.
Tums is an over-the-counter antacid whose active ingredient is calcium carbonate. It works by neutralizing existing stomach acid, which eases heartburn and acid indigestion, rather than reducing how much acid you make. The NHS notes that antacids and alginates are a common first step for indigestion and heartburn in pregnancy. Calcium carbonate also delivers calcium, which is why some prenatal guidance treats it as a dual-purpose option.
ACOG describes antacids as an appropriate part of managing heartburn in pregnancy, and calcium carbonate is commonly recommended as a preferred antacid because it is minimally absorbed into the bloodstream. The NHS lists calcium-containing antacids among options considered suitable during pregnancy when used as directed. There is no established evidence that normal-dose calcium carbonate harms a developing baby. Because the strongest guidance applies to occasional, label-dose use, we frame this as generally safe rather than risk-free.
Stay within the dose on the label, since excessive calcium can cause constipation and, rarely, high blood calcium. Separate Tums from your iron supplement by a couple of hours, as calcium can reduce iron absorption. The NHS suggests trying smaller, more frequent meals and avoiding trigger foods first; alginate antacids are another pregnancy-friendly option. Talk to your provider before regular daily use, if heartburn is severe or persistent, or before combining Tums with other supplements or medicines.