Angiotensin Antagonists


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.


Angiotensin II receptor antagonists should not be taken during pregnancy or while breastfeeding. When taken during pregnancy, they have been associated with causing severe health problems in babies, including improper kidney function, limb defects, incomplete skull development, underdeveloped lungs, birth defects in the heart, and death.

What are angiotensin II receptor antagonists?

Angiotensin II receptor antagonists, also called angiotensin II receptor blockers (ARBs), are heart medications that are used to lower your blood pressure. They also reduce strain on your heart and make it easier for your heart to pump blood. Types of ARBs that are available include: irbesartan (Avapro), losartan (Cozaar), valsartan (Diovan), candesartan (Atacand), olmesartan (Benicar), azilsartan (Edarbi), telmisartan (Micardis), and eprosartan (Teveten). These medications are only available by prescription from your doctor.

What are angiotensin II receptor antagonists used to treat?

ARBs are used to treat high blood pressure. They also reduce the chances of having a stroke or heart attack in people who have high blood pressure. In addition, they can be used as part of a treatment plan for people with heart failure and to protect the kidneys from injury in those who have type 2 diabetes. 

What is high blood pressure?

As blood flows through your body, it pushes on the walls of your blood vessels with a certain force. This force is called your blood pressure. High blood pressure occurs when this force is consistently higher than normal. It is often called a “silent killer” because some people have no symptoms and are unaware that they have this disease. Over time, high blood pressure can injure your heart and kidneys, or lead to a stroke or heart attack.

Expecting moms can develop high blood pressure during their pregnancy, even if they never had high blood pressure before. This type of high blood pressure usually starts after 20 weeks of pregnancy and disappears after your delivery. High blood pressure during pregnancy can sometimes cause complications, such as preeclampsia

How do angiotensin II receptor antagonists work?

ARBs block the actions of a hormone, called angiotensin II. Angiotensin II is responsible for increasing your blood pressure by making your blood vessels narrower and promoting the release of other chemicals that can further increase your blood pressure. By blocking the effects of angiotensin II, ARBs allow your blood vessels to expand. This lowers your blood pressure, improves blood flow, and reduces strain on the heart.

If I am taking an angiotensin II receptor antagonist, can it harm my baby?

ARBs can cause harm to your baby if you take them during pregnancy. All ARBs carry a black box warning, the strictest FDA warning for prescription drugs, because they have the potential to cause injury or death to the developing baby. This warning is particularly applicable when ARBs are taken during the second and third trimesters of pregnancy. ARBs can cross the placenta and interfere with proper functioning of the baby’s kidneys. They may also reduce the development of blood vessels in your baby’s head and interfere with blood flow in the placenta. These actions can lead to severe health problems in your baby, such as low blood pressure, incomplete development of the baby’s skull, lack of urine production, kidney failure, and death. ARBs can also lead to oligohydramnios, a condition where you have too little amniotic fluid. This can cause underdeveloped lungs and defects in the development of your baby’s bones. The FDA recommends that ARBs should be discontinued as soon as pregnancy is detected.

The following are some health problems that have been observed in babies whose mom used an ARB during any trimester of pregnancy:

  • Lack of urine production
  • Low blood pressure
  • Incomplete development of the skull
  • Birth defects in the heart
  • Premature birth
  • Intrauterine growth restriction (the baby is born smaller than normal)
  • Limb defects
  • Underdeveloped lungs
  • Kidney injury or failure
  • Oligohydramnios
  • Difficulty breathing
  • Problems with brain development
  • Miscarriage (death of the baby in the womb prior to 20 weeks of pregnancy), stillbirth (death of the baby in the womb after 20 weeks of pregnancy), or death after birth.

One review collected and described reports of the health problems listed above. There were 68 reports analyzed from expecting moms who had taken an ARB. Health problems were observed in 87% of babies born to these expecting moms. Although many reviews have associated harm when ARBs are used during the second and third trimesters of pregnancy, this review included 18 reports of expecting moms who used an ARB during the first trimester only. Eight of these babies did not have any complications, but the other 10 still developed health problems, despite only being exposed in the first trimester.

Bottom line: ARBs can cause harm to your baby and should not be used during any trimester of pregnancy.

If I am taking an angiotensin II receptor antagonist and become pregnant, what should I do?

If you become pregnant while taking an ARB, you should contact your doctor immediately. These medications could result in serious injury or death of your baby. The FDA recommends that these medications should be discontinued as soon as pregnancy is confirmed. Your doctor will likely discontinue your ARB until after the birth of your baby. In addition, for women who are planning to become pregnant and are taking an ARB, it is important to monitor your menstrual cycle. If your period is delayed by more than 2 days, you should contact your doctor immediately. Your doctor may decide to stop treatment with the ARB until you have a pregnancy test. Pregnancy tests should be repeated if your period has not started in a few days after the initial test.

If I am taking an angiotensin II receptor antagonist, can I safely breastfeed my baby?

There is no information available on the safety of ARBs while breastfeeding. They have the potential to cause harm to your baby by interfering with normal kidney function and blood pressure. For new moms who are taking an ARB, the FDA recommends that either nursing be discontinued, or the ARB be discontinued before you start breastfeeding.

Bottom line: ARBs should be avoided while breastfeeding. There is no data available on the effects of ARBs in the breastfed baby, but they have the potential to cause harm if the medication is passed to your baby in breast milk.

If I am taking an angiotensin II receptor antagonist, will it be more difficult to get pregnant?

There have been no studies looking at the effects of ARBs on a woman’s fertility, but there has been some limited evidence that ARBs may reduce fertility in men. One study tested 28 men who were taking an ARB and found that they had reduced concentrations of sperm, which could impact fertility. If your male partner is taking an ARB, he may consider contacting his doctor if he is having problems with fertility. In addition, women who are taking an ARB should contact their doctor prior to becoming pregnant. Your doctor may decide to switch you to an alternative medication to control your blood pressure.

If I am taking an angiotensin II receptor antagonist, what should I know?

ARBs should not be taken during pregnancy because they can cause serious harm to your baby. In general, ARBs are not recommended in women of childbearing age. Women who are taking an ARB should monitor their menstrual cycle carefully. If you notice a delay in your period of more than 2 days, you should contact your doctor immediately. Your doctor may decide
to immediately discontinue the ARB.

ARBs should not be used while breastfeeding. There is no evidence available on their safety in the breastfed infant, and they have the potential to cause problems with the baby’s kidney function and blood pressure.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of angiotensin II receptor antagonists during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry's expert reports about high blood pressure here, and hypertension here.  Additional information can also be found in the links below. 

For more information about angiotensin II receptor antagonists during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or check the following links:

Mayo Clinic: Angiotensin II receptor blockers
American Heart Association: The Facts About High Blood Pressure
American Heart Association: Why High Blood Pressure is a “Silent Killer.”
March of Dimes: High Blood Pressure During Pregnancy

Read the whole report
Last Updated: 29-11-2018
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.