Metoprolol and pregnancy. Let your doctor know if you are pregnant, might become pregnant, or are breastfeeding before taking metoprolol. There’s not enough evidence to say that metoprolol is safe during pregnancy, and pregnant women should take it only if there is a clear need. Metoprolol could also pass into breast milk, so ask your doctor about breastfeeding before taking metoprolol. There’s no evidence that metoprolol is safe or effective in children younger than 6 years old.