Oral pseudoephedrine (Sudafed) is best avoided in the first trimester and used with caution afterward. ACOG and the NHS advise against it in the first 13 weeks because of a possible link to a rare abdominal wall defect (gastroschisis), and it isn't recommended if you have high blood pressure since it can raise it. After the first trimester, occasional short-term use is generally considered acceptable for non-hypertensive women—check with your doctor or midwife first, and consider a saline spray or single-ingredient options as alternatives.
Sudafed is a brand name for pseudoephedrine, an oral decongestant used for a stuffy nose from colds, allergies, or sinus congestion. It works by narrowing blood vessels in the nasal passages. Because it acts on blood vessels throughout the body, it can also raise blood pressure and heart rate. Note that some products sold as "Sudafed PE" contain phenylephrine instead, which the FDA has found to be ineffective as an oral decongestant.
The CDC's National Birth Defects Prevention Study reported a possible small association between first-trimester pseudoephedrine use and defects such as gastroschisis, though the absolute risk is low and the evidence is not conclusive. ACOG and the NHS advise avoiding oral decongestants in early pregnancy for this reason, and also because pseudoephedrine can raise blood pressure. It is generally viewed as best avoided if you have high blood pressure or preeclampsia.
ACOG and the NHS often suggest non-drug measures first: saline nasal spray or rinses, a humidifier, staying hydrated, and elevating your head at night. For persistent symptoms, providers sometimes consider nasal sprays or, after the first trimester, certain oral options on a case-by-case basis. Always confirm the specific product and timing with your provider or pharmacist, since guidance can differ by trimester and by your blood pressure.