Pregnancy and ACE Inhibitors or ARBs: Fetal Risk and Safe Alternatives
Pregnancy Medication Safety Checker
This tool helps determine if your current blood pressure medication is safe during pregnancy and provides recommendations for safer alternatives.
When you're pregnant and managing high blood pressure, the medications you take aren't just about your health-they directly affect your baby's development. That's why ACE inhibitors and ARBs are never safe during pregnancy, no matter the trimester. These drugs, commonly prescribed for hypertension, heart failure, or kidney disease, can cause severe, sometimes fatal, harm to a developing fetus. Even if you're not trying to get pregnant, if you're taking one of these medications and could become pregnant, you need to know the risks-and what to do instead.
Why ACE Inhibitors and ARBs Are Dangerous in Pregnancy
ACE inhibitors (like lisinopril, enalapril, and captopril) and ARBs (like losartan and candesartan) work by blocking the renin-angiotensin-aldosterone system, or RAAS. This system helps control blood pressure, but in a growing baby, it’s essential for kidney development and amniotic fluid production. When this system is shut down by these drugs, the baby’s kidneys can’t function properly. That leads to low amniotic fluid (oligohydramnios), which can cause lung underdevelopment, limb contractures, and skull deformities. The baby’s blood pressure can drop dangerously low, kidneys can fail, and in severe cases, the pregnancy ends in miscarriage or stillbirth.
Studies show these risks aren’t rare. A 2011 study published in Obstetrics & Gynecology International found that women taking ACE inhibitors or ARBs during pregnancy had a 25.4% miscarriage rate-more than double the rate in women with similar health conditions who weren’t on these drugs. Babies exposed to these medications were also born, on average, 1.8 weeks earlier and weighed 350 grams less than babies not exposed. And while some early research suggested first-trimester exposure might be less risky, a 2020 meta-analysis of 72 studies concluded that even early exposure increases the chance of serious complications.
ARBs appear to be even more dangerous than ACE inhibitors. The American Heart Association found that babies exposed to ARBs had worse outcomes, including higher rates of neonatal death and kidney failure. That’s why doctors don’t just say “avoid these drugs”-they say “stop them immediately.”
What Happens If You’re Already Pregnant and Taking One of These Drugs?
If you find out you’re pregnant while taking an ACE inhibitor or ARB, don’t panic-but don’t wait either. Stop the medication right away and contact your doctor. The goal is to switch to a safer alternative as quickly as possible, ideally within days. The longer you stay on these drugs, the higher the risk to your baby, especially after the first trimester.
Doctors don’t just stop the drug and leave you untreated. High blood pressure during pregnancy can lead to preeclampsia, preterm birth, and placental problems. So switching to a safer medication is critical. The most commonly used and safest options are labetalol, methyldopa, and nifedipine.
Safe Blood Pressure Medications During Pregnancy
Not all blood pressure drugs are risky. Three medications have decades of safety data in pregnancy and are recommended by major medical groups like ACOG, the American Heart Association, and Health New Zealand.
- Labetalol: This beta-blocker is often the first choice. It works by slowing the heart and relaxing blood vessels. It’s been used safely since the 1970s, with no consistent link to birth defects. Starting doses are usually 100 mg twice daily, and doctors can increase it up to 2,400 mg per day if needed. It’s especially useful for women who also have heart rate issues.
- Methyldopa: This is the oldest and most studied blood pressure medication for pregnancy. It’s been used since the 1960s and has the longest safety record. It works by calming the nervous system to lower blood pressure. Typical starting dose is 250 mg twice daily, with doses going up to 3,000 mg per day. It’s often chosen for women with chronic hypertension who are planning pregnancy.
- Nifedipine: A calcium channel blocker, this is a good second-line option. It relaxes blood vessels and is especially helpful when labetalol or methyldopa aren’t enough. It’s not recommended for women with heart failure because it can weaken heart contractions. Extended-release forms are preferred to avoid sudden drops in blood pressure.
These drugs aren’t perfect-they can cause dizziness, fatigue, or headaches-but they don’t harm fetal development the way ACE inhibitors and ARBs do. Blood pressure targets during pregnancy are usually under 140/90 mmHg, unless there’s organ damage. The goal isn’t to get your numbers perfect-it’s to keep them stable and safe for your baby.
What About Planning Pregnancy?
If you’re taking an ACE inhibitor or ARB and thinking about getting pregnant, don’t wait until you miss your period. Talk to your doctor before you stop using birth control. Switching medications ahead of time gives your body time to adjust and reduces the chance of unplanned exposure.
Major health organizations now require doctors to ask women of childbearing age: “Are you planning to get pregnant?” and “Are you using reliable contraception?” If you’re on an ACE inhibitor or ARB, you should be. The U.S. FDA and the European Medicines Agency both require boxed warnings on these drugs for fetal risk. But even with warnings, about 1.2% of pregnant women with chronic hypertension are still exposed to these drugs-often because the switch wasn’t made early enough.
Doctors are now trained to do preconception counseling for women with high blood pressure. That means reviewing your meds, checking your blood pressure control, and switching to safer options before conception. If you’re on one of these drugs and haven’t had this conversation, ask for it.
Regulatory Warnings and Real-World Gaps
The FDA, EMA, WHO, and Medsafe all list ACE inhibitors and ARBs as contraindicated in pregnancy. The FDA used to classify them as Category D-meaning there’s clear evidence of fetal harm. Even after the labeling system changed in 2015, the warnings remain strong: these drugs carry a boxed warning for fetal toxicity. The World Health Organization doesn’t even include them in its list of essential medicines for pregnant women.
But guidelines don’t always reach patients. Some women don’t know their medication is risky. Others are afraid to stop their drug without another option. Some doctors don’t have time to switch prescriptions before pregnancy. That’s why it’s so important for you to know the risks. If your doctor prescribes an ACE inhibitor or ARB and you’re sexually active, ask: “Is this safe if I get pregnant?” If they say yes, get a second opinion.
What to Do Next
If you’re currently taking an ACE inhibitor or ARB:
- Don’t stop cold turkey without talking to your doctor-sudden withdrawal can spike your blood pressure.
- Ask if you’re on a safe alternative for pregnancy. If not, request a switch.
- If you’re planning pregnancy, schedule a preconception visit with your OB-GYN and cardiologist.
- Use reliable contraception if you’re not ready to get pregnant.
- If you’re already pregnant and on one of these drugs, call your provider immediately.
There’s no safe window for these medications during pregnancy. No trimester is risk-free. But the good news? There are safe, effective alternatives-and switching early makes all the difference.
Can I take ACE inhibitors or ARBs during the first trimester if I didn’t know I was pregnant?
No. Even first-trimester exposure carries risks. While early studies suggested the risk of major birth defects might be low, newer research shows increased chances of miscarriage, low birth weight, and preterm birth. Once you know you’re pregnant, stop the medication immediately and switch to a safer option like labetalol or methyldopa. The sooner you switch, the better the outcome for your baby.
Are there any exceptions where ACE inhibitors or ARBs might be used in pregnancy?
No. There are no safe exceptions. Every major medical organization worldwide-including ACOG, the American Heart Association, and the Society of Obstetricians and Gynaecologists of Canada-agrees that these drugs are absolutely contraindicated in all trimesters. Even in rare cases like severe preeclampsia or kidney disease, safer alternatives exist. Using these drugs in pregnancy is not medically justifiable.
What are the signs that a baby may have been affected by ACE inhibitors or ARBs?
Signs may show up on ultrasound: low amniotic fluid (oligohydramnios), poor kidney development, or skull abnormalities. After birth, symptoms can include low blood pressure, kidney failure, high potassium levels, and breathing problems. If you took one of these drugs during pregnancy, your baby’s care team will monitor for these issues closely. Early detection improves outcomes.
Can I breastfeed while taking labetalol or methyldopa?
Yes. Both labetalol and methyldopa are considered safe during breastfeeding. Very little of the medication passes into breast milk, and studies show no harmful effects on infants. Nifedipine is also generally considered safe. Always check with your doctor, but these are the preferred choices for nursing mothers with high blood pressure.
How often should blood pressure be checked during pregnancy if I’m on a safe medication?
If you’re on a safe blood pressure medication, your provider will likely check your blood pressure at every prenatal visit. If your numbers are stable, weekly or biweekly monitoring may be enough. If your blood pressure is hard to control or you have other risks like diabetes or kidney disease, you may need more frequent checks-even daily home monitoring. Keeping a log helps your doctor adjust your dose safely.