Plain Robitussin (guaifenesin) is generally considered low-risk in pregnancy, especially after the first trimester, and available data have not linked it to a clear increase in birth defects. Still, early-pregnancy evidence is limited, and many Robitussin products contain extra ingredients (alcohol, decongestants, cough suppressants) that change the picture. Guidance below reflects what ACOG, the NHS, and FDA labeling generally advise, but check with your own provider first.
Guaifenesin is an expectorant. It thins and loosens mucus so a chesty cough is easier to clear. "Robitussin" is a brand covering many formulas: some are plain guaifenesin, while others add dextromethorphan (a cough suppressant, sold as Robitussin DM), decongestants like phenylephrine or pseudoephedrine, or alcohol. The single active ingredient matters more than the brand name, so always read the label.
Studies to date have not shown a strong link between guaifenesin and birth defects, and reference sources like Drugs in Pregnancy and Lactation describe the fetal risk as low. However, first-trimester data are limited, so many clinicians suggest avoiding it in the first 12 weeks as a precaution and reserving it for later pregnancy if needed. ACOG makes no specific guaifenesin recommendation but considers dextromethorphan low-risk when used as directed.
If you use it, pick a single-ingredient product at the lowest effective dose and avoid liquid formulas that contain alcohol, which is not safe in pregnancy. Steer clear of multi-symptom combos and products with decongestants (phenylephrine, pseudoephedrine), especially in the first trimester, unless your clinician says otherwise. Non-drug options the NHS commonly suggests for coughs and colds include rest, plenty of fluids, honey and warm water, and steam inhalation.