Which medication is most commonly associated with gastrointestinal upset and constipation during pregnancy?

Ferrous sulfate is commonly associated with gastrointestinal upset and constipation during pregnancy due to its iron content. Iron supplements can cause various digestive issues, including nausea, vomiting, and constipation, because they can influence intestinal motility and can be irritating to the gastrointestinal lining.

During pregnancy, the demand for iron increases as it is essential for both maternal and fetal health, particularly for the formation of hemoglobin. However, the common side effects of ferrous sulfate can make adherence to the supplementation challenging for some women.

In contrast, calcium supplements, while they can also contribute to constipation, are generally less frequently reported for gastrointestinal upset when compared to iron supplements. Folic acid is crucial for fetal development and is usually well-tolerated without causing significant gastrointestinal issues. Cetirizine, an antihistamine, is primarily used to manage allergies and is not typically known to cause these types of gastrointestinal side effects.

Thus, ferrous sulfate stands out as the medication most frequently linked to gastrointestinal upset and constipation during pregnancy.