Metoprolol is not considered dangerous during pregnancy, but it does carry some risks that require careful monitoring. Published observational studies have not found an association between metoprolol and major birth defects or miscarriage. However, it has been linked to reduced fetal growth and a small increase in certain complications for newborns, particularly when used in the second and third trimesters. For many pregnant women with heart conditions or high blood pressure, the benefits of controlling those conditions outweigh the risks of the medication itself.
What the Safety Data Shows
The FDA-approved labeling for metoprolol states that available data from observational studies have not demonstrated a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. The background risk of major birth defects in any pregnancy is 2 to 4%, and the background risk of miscarriage is 15 to 20%. Metoprolol does not appear to raise those numbers.
Where the picture gets more complicated is with fetal growth. One study comparing long-term beta-blocker exposure (metoprolol or bisoprolol) during the second and third trimesters found that 24.1% of exposed infants were born small for gestational age, compared with 10.2% of infants whose mothers took a different blood pressure medication (methyldopa) and 9.9% of infants born to mothers without hypertension. It remains unclear how much of this effect comes from the medication versus the underlying condition being treated, since high blood pressure itself restricts fetal growth.
Risks to the Newborn
Metoprolol crosses the placenta, which means the baby is exposed to the drug’s effects before birth. Beta-blocker exposure late in pregnancy can cause temporary problems in newborns, including low blood sugar, slow heart rate, and low blood pressure. A large study found that neonatal low blood sugar occurred in 4.3% of beta-blocker-exposed newborns versus 1.2% of unexposed newborns. Slow heart rate occurred in 1.6% of exposed infants compared with 0.5% of unexposed infants.
These complications are typically manageable. Medical teams expect them and monitor for them. A baby born to a mother taking metoprolol will generally receive extra observation after delivery, including blood sugar checks and heart rate monitoring. In most cases, these issues resolve on their own within the first day or two of life.
Why It’s Still Prescribed During Pregnancy
Uncontrolled high blood pressure during pregnancy raises the risk of preeclampsia, gestational diabetes, premature delivery, and the need for cesarean section. For the baby, untreated maternal hypertension increases the risk of growth restriction and stillbirth. In many cases, the danger of leaving these conditions untreated is greater than the risks associated with metoprolol.
Metoprolol is commonly prescribed for pregnant women with heart disease. In Norway, it is the recommended drug of choice for pregnant women with cardiac conditions, and more than 86% of pregnant women on beta-blockers in one large Norwegian study were taking metoprolol. It is also a preferred option for treating abnormal heart rhythms during pregnancy, alongside propranolol.
How It Compares to Other Options
Labetalol is the most commonly prescribed beta-blocker in pregnancy overall and is often considered the first-line choice for managing high blood pressure. It works slightly differently from metoprolol, blocking both beta and alpha receptors, which helps reduce resistance in blood vessels. Nifedipine (a calcium channel blocker) and methyldopa are also frequently used alternatives.
Interestingly, the data on fetal growth restriction doesn’t clearly favor labetalol over metoprolol. One large retrospective study of nearly 380,000 pregnancies found that labetalol and atenolol were associated with increased risk of small-for-gestational-age babies, while metoprolol and propranolol were not. A narrative review of the literature concluded that beta-1 selective blockers like metoprolol are associated with a lower incidence of adverse outcomes and are preferred for first-line therapy in pregnancy (with the exception of atenolol, which carries more risk). So while labetalol is more widely used, metoprolol may actually perform favorably in some comparisons.
Your Body Processes It Differently During Pregnancy
Pregnancy changes how your body breaks down metoprolol, and this matters for whether the dose you’re on will keep working. The liver enzyme responsible for metabolizing metoprolol becomes significantly more active during pregnancy. In one pharmacokinetic study, the rate at which pregnant women cleared metoprolol from their bodies nearly tripled by late pregnancy compared to postpartum levels.
This means a dose that controlled your blood pressure or heart rate before pregnancy may become less effective as your pregnancy progresses. If you notice your symptoms returning or your blood pressure readings climbing, your provider may need to increase your dose or adjust how often you take it. After delivery, your metabolism returns to its pre-pregnancy baseline, so doses typically need to be reduced again postpartum to avoid overmedication.
Safety During Breastfeeding
Metoprolol passes into breast milk in very small amounts. The average relative infant dose is about 0.5% of the mother’s weight-adjusted dose, which is well below the 10% threshold generally considered the cutoff for concern. Studies on metoprolol use during breastfeeding have found no adverse reactions in breastfed infants. It has low bioavailability, a short half-life, and is widely regarded as compatible with nursing.