13 Medications You Should Absolutely Avoid While Pregnant

A mother's bond to her baby (and vice versa) is unlike any other. While growing inside the womb, babies continuously rely on their mothers for survival. The pair is connected via the placenta, through which the baby receives oxygen, nutrients, and antibodies. The baby also forms waste and other harmful substances even inside the womb, which is filtered out through the placenta and goes to the mother's system to get excreted out of the body (per Cleveland Clinic).

There are many things expectant mothers need to be aware of in order to ensure that their pregnancy progresses smoothly and without any complications. This can become really overwhelming, especially for first-time mothers. Some of these include which food and beverages they can and cannot consume, what kinds of physical activity they should and should not do, how often they should go to doctor's appointments, and what medications are safe or harmful to them and/or their unborn baby.

As helpful as medications are in treating and managing health conditions, their possible side effects can make taking them an unpleasant experience for the general population. In pregnant women, not only do they have to worry about side effects like everyone else, but they also have to take into consideration how medications will affect their pregnancy. This is especially challenging for pregnant women who have chronic conditions, since they usually need to be on medication long-term.

Drugs that can cause damaging effects to a fetus are called teratogenic. Below are some common examples.

Both angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are classes of drugs used to treat high blood pressure. According to UpToDate, they are considered as first-line treatment, which means that they are the first drugs a doctor will prescribe to their hypertensive patients. Examples of ACE inhibitors are lisinopril, benazepril, and captopril; ARBs include losartan, valsartan, and telmisartan.

GoodRx warns that ACE inhibitors and ARBs should never be taken during pregnancy. They can affect the development and function of your unborn baby's kidneys, especially if you take them during the second and third trimesters. Consequently, damage to their kidneys can decrease the amount of amniotic fluid that surrounds and protects them, which can ultimately lead to birth defects or even death. If you have been taking ACE inhibitors or ARBs for hypertension and you become pregnant, let your doctor know right away so that they can switch you to a safer medication for your baby that's equally effective in controlling your blood pressure. Depending on your specific situation, you may be prescribed labetalol, nifedipine, methyldopa, or hydrochlorothiazide, per recommendations from the American Academy of Family Physicians.

Hypertension can also develop as a consequence of changes during pregnancy. If this happens, a pregnant woman may be diagnosed with gestational hypertension, pre-eclampsia, or eclampsia, depending on the disease's severity. According to the Journal of the American Heart Association, management of these conditions depends on how bad the disease is, but if medications need to be given, the same ones mentioned above are typically used.

Methotrexate has gained popularity over the years for its use in medically induced abortions. With the most recent abortion ban controversy, several reports have stated that it has become harder to get access to methotrexate, even in women who have chronic conditions that can only be treated with the drug.

Drugbank Online explains that methotrexate works by inhibiting the synthesis of DNA, thus effectively preventing the division of cells. It is often prescribed for conditions that cause rapid and uncontrolled cell production, including certain types of cancers (e.g., leukemia, lymphoma, osteosarcoma, breast cancer, bladder cancer), Crohn's disease, severe psoriasis, multiple sclerosis, rheumatoid arthritis, and graft rejection (i.e., graft-versus-host disease).

Methotrexate has many associated side effects, which is why it is only prescribed when it is absolutely necessary. Couples who are planning to get pregnant and women who are already pregnant should stay away from methotrexate to avoid causing harm to the developing fetus. Methotrexate can lead to a number of birth defects like spina bifida, cleft palate, and teeth and bone abnormalities, but they can also lead to death of the unborn baby (via Medical News Today). Before trying to get pregnant, men should be off of methotrexate for at least three months, and women should wait for at least one menstrual cycle to finish. To avoid accidental pregnancies, couples are often advised to use effective measures of birth control like proper and consistent condom use, birth control pills, and intrauterine device (IUD) insertions.

Isotretinoin is a prescription-only medication made from synthetic vitamin A, used to treat severe and persistent acne. Per WebMD, it effectively decreases oil production, which helps prevent plugging of follicles. Plugged follicles coupled with bacterial colonization is the main mechanism behind acne development. While highly effective for acne, it is also very harmful to an unborn baby. 

March of Dimes states that taking isotretinoin during pregnancy can lead to miscarriages and premature births, as well as several other complications like cleft palate, congenital heart defects, small eyes, small ears, small head, parathyroid dysfunction, physical disabilities, and intellectual disability. Because of the risks, the use of isotretinoin is heavily regulated. Women who are pregnant are not allowed to take the drug, and women who are able to get pregnant are required to be on two forms of birth control (primary and secondary), as well as have two negative pregnancy tests regularly. Primary forms of birth control include IUDs, hormonal birth control, estrogen-containing birth control pills, tubal ligation, and vasectomy. Secondary forms include male condoms, cervical cap with spermicide, diaphragm with spermicide, and vaginal sponge with spermicide (per Drugs.com).

All patients who are on isotretinoin are enrolled in the iPLEDGE Program, a centralized system that aims to minimize the risk of isotretinoin-related pregnancy complications. Isotretinoin can only be given through this program, which means that only providers and pharmacies enrolled in this program are allowed to prescribe and dispense isotretinoin, and only enrolled patients are allowed to receive it.

Warfarin is a common drug prescribed for the treatment and prevention of blood clots. It is also used to reduce the risk of recurrent strokes and mini-strokes. Additionally, in people who have experienced a heart attack, warfarin can decrease the risk of death, repeat heart attacks, and other complications. It works by inhibiting the activation of vitamin K, which is essential in the synthesis of factors that cause blood to clot. Warfarin effectively serves as an anticoagulant or blood thinner (via StatPearls).

According to Medscape, pregnant women are naturally at an increased risk of developing blood clots in their veins, which is why it is sometimes necessary to give anticoagulant therapy, especially if they have any underlying conditions that can further increase their risk. These conditions include valvular heart defects, antiphospholipid syndrome (APAS), factor V Leiden, and antithrombin deficiency. However, according to an article from the Journal of Obstetrics and Gynecology Canada, warfarin can easily cross the placenta, and when it does, it prevents the fetus from synthesizing proteins that are essential for proper development of their bones and cartilage. When taken during the first trimester, it can also lead to spontaneous abortions, stillbirths, preterm birth, and nervous system abnormalities. 

Because of this, warfarin is never given to pregnant women. Instead, they are given heparin. Exceptions to this are pregnant women with mechanical heart valves. In this scenario, warfarin is more effective than heparin, so the decision is dependent upon whether the benefits of warfarin therapy outweighs the risks.

Ativan (lorazepam), Valium (diazepam), or Xanax (alprazolam) may sound familiar: Perhaps you or someone you know have previously used them to help with sleep, anxiety, seizures, or even withdrawal from alcohol. These are just some examples of the many benzodiazepines currently approved for use in the United States. All are prescription-only and classified as controlled substances (per Cleveland Clinic). According to the United States Drug Enforcement Administration (DEA), controlled substances are drugs that need to be regulated by the government because of safety reasons and their potential to cause addiction. Aside from benzodiazepines, other examples include GHB ("date rape" drug), LSD ("acid"), and MDMA (ecstasy or molly).

Benzodiazepines work by increasing the levels of a neurotransmitter called gamma-aminobutyric acid or GABA (via Caron). GABA inhibits nerve signals, thus effectively slowing down the functions of the nervous system. Benzodiazepines are very effective drugs, but can cause addiction rather quickly (after at least four weeks of daily use). Moreover, combining benzodiazepines with alcohol (another nervous system depressant) can lead to fatal complications.

According to the American Addiction Centers, benzodiazepines are contraindicated in pregnancy because they can easily cross the placenta and lead to preterm birth, a higher risk of cesarean section, low birth weight, cleft lip and palate, and breathing problems associated with a greater chance of needing ventilatory support after birth. A newborn can also develop withdrawal symptoms like fussiness, irritability, sleep problems, tremors, and seizures.

If you or anyone you know needs help with addiction issues, help is available. Visit the Substance Abuse and Mental Health Services Administration website or contact SAMHSA's National Helpline at 1-800-662-HELP (4357).

Anticonvulsants (antiepileptic drugs or AEDs) are used to treat or prevent seizures. They are also sometimes used to treat nerve pain and bipolar disorder. Many drugs are classified under anticonvulsants, including carbamazepine, valproic acid, lithium, phenytoin, and lamotrigine. Benzodiazepines and phenobarbital are also considered as anticonvulsant drugs. Most AEDs work by increasing GABA, or inhibiting sodium or calcium channels; in some drugs, the mechanism is still unclear.

Per the Epilepsy Foundation, exposure to anticonvulsants occurs in as much as 1 out of 50 pregnancies. This is unavoidable, especially since epilepsy is a chronic condition that needs to be controlled with medication. Pregnancy also increases the risk of seizure episodes, particularly in women who did not have their seizures under control prior to getting pregnant. Managing seizures during pregnancy becomes even more challenging because AED levels drop significantly due to increased metabolism and excretion by the liver and kidneys.

Unfortunately, several types of anticonvulsants can cause harm to unborn babies when taken during pregnancy, including valproate, phenobarbital, carbamazepine, phenytoin, and topiramate. They can cause intellectual disability in low doses; high doses can lead to structural abnormalities like neural tube defects, facial dysmorphisms, absent limbs, heart defects, and impaired growth (via StatPearls).

Because pregnant women with active seizure disorders need to be on medication, doctors frequently monitor drug levels and watch out for side effects. Women on AEDs are also supplemented with folate before and during pregnancy to help protect their babies from developing birth defects (per the Epilepsy Foundation).

Nonsteroidal anti-inflammatory drugs (NSAIDs) are probably some of the most commonly used over-the-counter medications. According to SingleCare, they work by decreasing the production of substances called prostaglandins, which are compounds that can induce pain and inflammation. OTC NSAIDs are frequently marketed for use to temporarily relieve or reduce headaches, muscle aches, arthritic pain, back aches, fevers, and menstrual cramps. The most common ones include aspirin, ibuprofen (e.g., Advil, Motrin), naproxen (e.g., Aleve), celecoxib (e.g., Celebrex), and diclofenac (e.g., Voltaren).

In recent years, the U.S. Food & Drug Administration (FDA) has recommended that pregnant women avoid using NSAIDs, specifically at 20 weeks and onwards. Although rare, studies show that NSAIDs can affect proper kidney function and development, leading to low levels of amniotic fluid. Adequate amount of amniotic fluid is necessary for the protection of fetuses inside the womb, and helps with the development of muscles, the lungs, and the gastrointestinal system. If it is absolutely necessary for you to take NSAIDs (e.g., aspirin for high blood pressure), your doctor will likely prescribe you with the lowest effective dose for your condition, for the shortest possible period of time.

UT Southwestern Medical Center suggests using alternatives to NSAIDs for OTC uses, such as acetaminophen (e.g., Tylenol). Before buying OTC drugs, always read the ingredients list carefully, to make sure that you are not buying combination drugs that may contain NSAIDs or other drugs that can be harmful to you or your unborn baby.

Thalidomide was initially marketed in the 1950s as a sedative and for the treatment of morning sickness in pregnant women (via StatPearls). However, not long after, it was discovered that it actually caused significant harm to fetuses, leading to absent or inadequately formed limbs and internal organ abnormalities. During that time, no one knew exactly how the drug worked, so it was banned for use until it made its comeback in the 1990s. New research on the drug showed that it was actually effective in the treatment of multiple myeloma, as well as several other immune system disorders.

According to Mayo Clinic, because of the potent effects of thalidomide on the developing fetus, reproductive-age women who are prescribed the drug are required by the FDA to be counseled on its possible side effects, sign a consent form, undergo regular pregnancy tests, and be on multiple forms of birth control.

If you are on thalidomide and you become pregnant, speak with your doctor right away. You will need to stop taking the drug and be put on another alternative treatment. According to Drugs.com, alternatives to thalidomide for multiple myeloma treatment include daratumumab (Darzalex) and belantamab mafodotin (Blenrep). Both of these drugs can also possibly cause harm to unborn babies; unfortunately, the risk has not yet been extensively studied. Multiple myeloma can also be treated using chemotherapy, radiation therapy, corticosteroids, and bone marrow transplant (per Cleveland Clinic).

Bacterial infections are common and many in number, so it only makes sense for there to also be a mountain of drugs available to help treat them. The type of antibiotic prescribed is largely dependent on the type of bacteria causing the infection and whether it is susceptible or resistant to its usual treatment. Antibiotics can have a wide range of side effects, some unique to their specific drug class. Antibiotics that are established to be harmful during pregnancy include aminoglycosides, tetracyclines, and fluoroquinolones (per WebMD).

According to Medscape, aminoglycosides like streptomycin, gentamicin, and tobramycin have been reported to cause hearing defects, balance problems, and inner ear damage in babies whose mothers took the drug during pregnancy. Additionally, pregnant women who took tetracyclines (e.g., doxycycline) during their second or third trimesters were reported to have babies with permanently discolored teeth. Fluoroquinolones such as ciprofloxacin and levofloxacin can also possibly harm fetuses based on animal studies, and should therefore also be avoided during pregnancy unless absolutely necessary.

Although it may seem like many antibiotics are contraindicated for use during pregnancy, there are several other classes of antibiotics that can be used to treat bacterial infections. It is important to note, however, that resistance to antibiotics continues to rise. You should only be taking antibiotics for its intended use, and only when it is indicated and properly prescribed by your doctor.

Getting a cancer diagnosis has long been associated with a feeling of dread and fear. However, gone are the days when cancer automatically means receiving a death sentence. With advancements in treatment and earlier detection through screening tests, the number of people who survive cancer has been steadily increasing. According to the latest data provided by the Centers for Disease Control and Prevention (CDC), death rates due to cancer have dropped 27% from 2001 to 2020.

Unfortunately, although there are now more options in cancer treatment, they are not without their risks. During the earlier stages of pregnancy, chemotherapy and radiation therapy are typically avoided because they can cause birth defects or even death of the fetus (per Cancer.net). According to the American Cancer Society, the most common cancers detected during pregnancy are not that different from the cancers usually found in young women, and include breast, cervical, and thyroid cancer.

Based on a 2021 review in Cancers, there are limited data regarding the effect of cancer treatment during pregnancy, given that it is neither ideal nor ethical to perform clinical studies on pregnant women and fetuses. All chemotherapy drugs are able to cross the placenta in theory, but based on the researchers' study results, some chemotherapy drugs seem to be safe for use during pregnancy. Anticancer drugs that were found to be contraindicated during pregnancy (or have uncertain effects) include fluorouracil, tamoxifen, HER2-targeted therapies (e.g., trastuzumab, pertuzumab), ipilimumab, protein kinase inhibitors (e.g., erlotinib), and ifosfamide.

The thyroid gland is a small, two-lobed organ that can be found in the neck. It secretes thyroid hormones, which control how fast or how slow metabolic processes in the body take place (per Merck Manual). According to the American Thyroid Association, it is estimated that more than 12% of Americans will develop some form of thyroid disease at some point in their lives, 60% of whom will not even know that they have it. Thyroid disease can generally be classified as either having an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism). Hypothyroidism is treated using natural or synthetic thyroid hormones; hyperthyroidism is treated with medications that can suppress thyroid hormone production.

Hypothyroid medications are typically safe for use during pregnancy, but the same cannot be said for drugs used to treat hyperthyroidism. These include methimazole, carbimazole, propylthiouracil (PTU), and radioactive iodine. Technically, methimazole, carbimazole, and PTU can be used during pregnancy; however, timing is crucial. Methimazole and carbimazole are not given to pregnant women during their first trimester because they have a rare tendency to cause birth defects, so PTU is used instead (via Medicines in Pregnancy). On the other hand, PTU can be toxic to the liver, so pregnant women are typically switched back to methimazole after the first trimester (per Drugs.com).

According to MotherToBaby, radioactive iodine should never be used during pregnancy, as this can destroy the fetus' thyroid cells and impair proper development. Additionally, all antithyroid medications can cause a baby to develop hypothyroidism, learning disabilities, and behavioral problems.

Malaria is an infectious (but not contagious) disease carried by mosquitoes. Every year, around 2,000 cases of malaria are reported in the United States, the majority of which come from people who recently traveled to countries where malaria is endemic (per the CDC).

Primaquine is one of the medications used to treat, manage, or prevent malaria; it is also sometimes used together with the antibiotic clindamycin to treat pneumocystis pneumonia in people with AIDS (via Medscape). It cannot be given to women who are pregnant, because according to the FDA, primaquine can cause hemolytic anemia in people who have underlying glucose-6-phosphate dehydrogenase (G6PD) deficiency. Even if a pregnant woman does not have G6PD deficiency, there is a chance that their unborn baby does. Additionally, studies on bacteria and animals show that it can cause genetic mutations, DNA damage, and harm to developing animal fetuses and embryos. If any man or woman who is capable of reproduction needs to be on primaquine, they need to use (or be on) effective birth control, and women specifically need to have a negative pregnancy test before they start treatment.

Untreated malaria during pregnancy can lead to several complications, including maternal anemia, premature delivery, stillbirths, miscarriages, and low birth weight. Management of malaria depends on many factors, but in general, anti-malarial drugs that are considered safe for use during pregnancy include artemether-lumefantrine, clindamycin with quinine, and chloroquine.

Medications used to treat people with human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) are called antiretrovirals. According to HIV.gov, all pregnant women who are HIV-positive should be on a regimen of antiretroviral drugs, regardless of how well-controlled their disease is. Unfortunately, there are very few clinical trials on antiretrovirals that include pregnant women in their studies, so the safety and efficacy of these drugs in this specific population are not as well-established. In addition, treatment of HIV and AIDS typically involve a combination of several drugs, because there is no one specific regimen that works for all. Therefore, if you are already on an effective and well-tolerated antiretroviral regimen and you become pregnant, you will most likely continue the same regimen, but only if it is deemed safe for you and your unborn baby by your doctor.

According to Medscape, out of the many antiretrovirals available for use, didanosine showed the greatest risk of birth defects, regardless of how far along into the pregnancy it was taken. In animal studies, efavirenz also showed a potential to cause severe malformations when given during the first trimester. Human studies so far have not shown the same effect. Similarly, animal studies using tenofovir showed growth restriction and decreased bone porosity in fetuses, but results from available human studies so far have been conflicting.

Consult with your doctor or pharmacist if you are pregnant (or planning to get pregnant) and are unsure about taking any medication or supplement.