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Drug Use During Pregnancy

By

Ravindu Gunatilake

, MD, Valley Perinatal Services;


Avinash S. Patil

, MD, University of Arizona

Last full review/revision Feb 2021| Content last modified Feb 2021
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More than 50% of pregnant women take prescription or nonprescription (over-the-counter) drugs or use social drugs (such as tobacco and alcohol) or illicit drugs at some time during pregnancy, and use of drugs during pregnancy is increasing. In general, drugs should not be used during pregnancy unless necessary because many can harm the fetus. Less than 2 to 3% of all birth defects result from drugs that are taken to treat a disorder or symptom.

Sometimes drugs are essential for the health of the pregnant woman and the fetus. In such cases, a woman should talk with her doctor or other health care practitioner about the risks and benefits of taking the drug. Before taking any drug (including over-the-counter drugs) or dietary supplement (including medicinal herbs), a pregnant woman should consult her health care practitioner. A health care practitioner may recommend that a woman take certain vitamins and minerals during pregnancy.

Drugs taken by a pregnant woman reach the fetus primarily by crossing the placenta, the same route taken by oxygen and nutrients, which are needed for the fetus's growth and development. However, drugs that do not cross the placenta may still harm the fetus by affecting the uterus or the placenta.

Drugs that a pregnant woman takes during pregnancy can affect the fetus in several ways:

How Drugs Cross the Placenta

Some of the fetus's blood vessels are contained in tiny hairlike projections (villi) of the placenta that extend into the wall of the uterus. The mother's blood passes through the space surrounding the villi (intervillous space). Only a thin membrane (placental membrane) separates the mother's blood in the intervillous space from the fetus's blood in the villi. Drugs in the mother's blood can cross this membrane into blood vessels in the villi and pass through the umbilical cord to the fetus.

How Drugs Cross the Placenta

How a drug affects a fetus depends on

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Until recently, the Food and Drug Administration (FDA) classified drugs into five categories according to the degree of risk they pose for the fetus if they are used during pregnancy. Drugs were classified from those with the least risk to those that are highly toxic and should never be used by pregnant women because they cause severe birth defects. One example of a highly toxic drug is thalidomide. This drug causes extreme underdevelopment of arms and legs and defects of the intestine, heart, and blood vessels in the babies of women who take the drug during pregnancy.

The FDA's classification system was based largely on information from studies in animals, which often do not apply to people. For example, some drugs (such as meclizine) cause birth defects in animals, but the same effects have not been seen in people. Taking meclizine for nausea and vomiting during pregnancy does not appear to increase the risk of having a baby with a birth defect. The classification system was based much less often on well-designed studies in pregnant women because few such studies have been done. Thus, applying the classification system in specific situations was difficult.

Because of this problem, the FDA eliminated the five risk categories. Instead, the FDA now requires that the drug label include more information about the risk of taking every drug during pregnancy. This information includes the following:

  • The risks of taking the drug during pregnancy and breastfeeding

  • The evidence that has identified these risks

  • Information to help health care practitioners decide whether the drug should be used during pregnancy and to help them explain the risks and benefits of using the drug to the woman

Typically, health care practitioners follow a general rule:

  • They consider giving a pregnant woman a drug to treat a disorder only when the potential benefit outweighs known risks.

Often, a safer drug can be substituted for one that is likely to cause harm during pregnancy. For prevention of blood clots, the anticoagulant heparin is preferred to warfarin. Several safe antibiotics, such as penicillin, are available to treat infections.

Some drugs can have effects after they are stopped. For example, isotretinoin, a drug used to treat skin disorders, is stored in fat beneath the skin and is released slowly. Isotretinoin can cause birth defects if women become pregnant within 2 weeks after the drug is stopped. Therefore, women are advised to wait at least 3 to 4 weeks after the drug is stopped before they become pregnant.

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Vaccines During Pregnancy

COVID-19 vaccines are recommended for pregnant women and given based on the priority groups established by the Centers for Disease Control and Prevention (CDC) and the Advisory Committee on Immunization Practices (ACIP).

Drugs Used to Treat Heart and Blood Vessel Disorders During Pregnancy

Several types of antihypertensives, such as angiotensin-converting enzyme (ACE) inhibitors and thiazide diuretics, are usually not given to pregnant women. These drugs can cause serious problems in the fetus, such as kidney damage, inadequate growth before birth (growth restriction Small-for-Gestational-Age (SGA) Newborn A newborn who weighs less than 90% of newborns of the same gestational age at birth (below the 10th percentile) is considered small for gestational age. Newborns may be small because their parents... read more ), and birth defects. Spironolactone is also not given to pregnant women. This drug may cause the development of feminine characteristics (feminization) in a male fetus.

Antidepressants During Pregnancy

Antidepressants Drug therapy for depression A short discussion of prolonged grief disorder. Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to... read more , particularly selective serotonin reuptake inhibitors (SSRIs) such as paroxetine, are commonly used during pregnancy. Use is common because about 7 to 23% of pregnant women have depression. For pregnant women, the benefits of treating depression usually outweigh the risks.

Paroxetine appears to increase the risk of heart birth defects. So if a pregnant woman takes paroxetine, echocardiography should be done to evaluate the fetus's heart. However, other SSRIs do not increase this risk.

If a pregnant woman takes antidepressants, the newborn may have withdrawal symptoms (such as irritability and shaking) after delivery. To prevent these symptoms, doctors may gradually reduce the dose of the antidepressant during the 3rd trimester and stop the drug before the baby is born. However, if the woman has significant signs of depression or if symptoms worsen as the dose is reduced, antidepressants should be continued. Depression during pregnancy can lead to postpartum depression Postpartum Depression Postpartum depression is a feeling of extreme sadness and related psychologic disturbances during the first few weeks or months after delivery. Women who have had depression are more likely... read more , which involves a serious change in mood and requires treatment.

Antiviral Drugs During Pregnancy

Some antiviral drugs (such as zidovudine and ritonavir for HIV infection) have been safely used during pregnancy for many years. However, some antiviral drugs may cause problems in the fetus. For example, some evidence suggests that when some HIV regimens with a combination of antiviral drugs are given during the 1st trimester, the risk of cleft lip and palate may be increased.

If a pregnant woman gets COVID-19, her treatment team and she should discuss the risks and benefits for her and then decide whether remdesivir should be used to treat COVID-19. Generally, experts recommend that theoretical concerns about the safety of remdesivir during pregnancy should not prevent its use in pregnant women. There are little data about the effects of remdesivir on the fetus.

If a pregnant woman gets influenza, she should seek treatment as soon as possible because treating influenza within 48 hours of when symptoms begin is most effective. However, treatment at any point during the infection reduces the risk of severe complications. No well-designed studies of zanamivir and oseltamivir have been done in pregnant women. However, many studies based on observation indicate that treating pregnant women with zanamivir or oseltamivir does not increase the risk of harmful effects. There is little or no information about the use of other influenza drugs during pregnancy.

Acyclovir, taken by mouth or applied to the skin, appears to be safe during pregnancy.

Social Drugs During Pregnancy

Cigarette (tobacco) smoking during pregnancy

The most consistent effect of smoking on the fetus during pregnancy is

The more a woman smokes during pregnancy, the less the baby is likely to weigh. The average birth weight of babies born to women who smoke during pregnancy is 6 ounces less than that of babies born to women who do not smoke.

Birth defects of the heart, brain, and face are more common among babies of smokers than among those of nonsmokers.

Also, the risk of the following may be increased:

In addition, children of women who smoke have slight but measurable deficiencies in physical growth and in intellectual and behavioral development. These effects are thought to be caused by carbon monoxide and nicotine. Carbon monoxide may reduce the oxygen supply to the body's tissues. Nicotine stimulates the release of hormones that constrict the vessels supplying blood to the uterus and placenta, so that less oxygen and fewer nutrients reach the fetus.

Because of the possible harmful effects of smoking during pregnancy, pregnant women should make every effort to not smoke during pregnancy, including discussing strategies with their doctor.

Pregnant women should avoid exposure to secondhand smoke because it may similarly harm the fetus.

Alcohol during pregnancy

Drinking alcohol Alcohol Alcohol (ethanol) is a depressant. Consuming large amounts rapidly or regularly can cause health problems, including organ damage, coma, and death. Genetics and personal characteristics may... read more during pregnancy is the leading known cause of birth defects. Because the amount of alcohol required to cause fetal alcohol syndrome is unknown, pregnant women are advised to abstain from drinking any alcohol regularly or on binges. Avoiding alcohol altogether is even safer.

Did You Know...

  • The leading known cause of birth defects is drinking alcohol during pregnancy.

Often, the birth weight of babies born to women who drink regularly during pregnancy is substantially below normal. The average birth weight is about 4 pounds for babies exposed to large amounts of alcohol, compared with 7 pounds for all babies. Newborns of women who drank during pregnancy may not thrive and are more likely to die soon after birth.

Fetal alcohol syndrome is one of the most serious consequences of drinking during pregnancy. Binge drinking as few as three drinks a day can cause this syndrome. It occurs in about 2 of 1,000 live births. This syndrome includes the following:

Babies or children of women who drank alcohol during pregnancy may have severe behavioral problems, such as antisocial behavior and attention-deficit/hyperactivity disorder Attention-Deficit/Hyperactivity Disorder (ADHD) Attention-deficit/hyperactivity disorder (ADHD) is poor or short attention span and/or excessive activity and impulsiveness inappropriate for the child’s age that interferes with functioning... read more . These problems can occur even when the baby has no obvious physical birth defects.

Caffeine during pregnancy

Whether consuming caffeine during pregnancy harms the fetus is unclear. Evidence seems to suggest that consuming caffeine in small amounts (for example, one cup of coffee a day) during pregnancy poses little or no risk to the fetus.

Caffeine, which is contained in coffee, tea, some sodas, chocolate, and some drugs, is a stimulant that readily crosses the placenta to the fetus.

Some experts recommend limiting coffee consumption and drinking decaffeinated beverages when possible.

Aspartame during pregnancy

Aspartame, an artificial sweetener, appears to be safe during pregnancy when it is consumed in small amounts, such as in amounts used in normal portions of artificially sweetened foods and beverages. For example, pregnant women should consume no more than 1 liter of diet soda a day.

Illicit Drugs During Pregnancy

Use of illicit drugs (particularly opioids) during pregnancy can cause complications during pregnancy and serious problems in the developing fetus and the newborn. For pregnant women, injecting illicit drugs increases the risk of infections that can affect or be transmitted to the fetus. These infections include hepatitis Overview of Hepatitis Hepatitis is inflammation of the liver. (See also Overview of Acute Viral Hepatitis and Overview of Chronic Hepatitis.) Hepatitis is common throughout the world. Hepatitis can be Acute (short-lived) read more and HIV infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more Human Immunodeficiency Virus (HIV) Infection (including AIDS). Also, when pregnant women take illicit drugs, growth of the fetus is more likely to be inadequate, and premature births are more common.

Amphetamines during pregnancy

Bath salts during pregnancy

Cocaine during pregnancy

Cocaine Cocaine Cocaine is an addictive stimulant drug made from leaves of the coca plant. Cocaine is a strong stimulant that increases alertness, causes euphoria, and makes people feel powerful. High doses... read more taken during pregnancy may cause the blood vessels that carry blood to the uterus and placenta to narrow (constrict). Then, less oxygen and fewer nutrients reach the fetus.

If pregnant women use cocaine regularly, risk of the following is increased:

However, whether cocaine is the cause of those problems is unclear. For example, the cause may be other risk factors that are common in women who use cocaine. Such factors include cigarette smoking, use of other illicit drugs, deficient prenatal care, and poverty.

Hallucinogens during pregnancy

Marijuana during pregnancy

Whether use of marijuana Marijuana Marijuana (cannabis) is a drug made from the plants Cannabis sativa and Cannabis indica that contain a psychoactive chemical called delta-9-tetrahydrocannabinol (THC). Marijuana produces a dreamy... read more during pregnancy can harm the fetus is unclear. The main component of marijuana, tetrahydrocannabinol, can cross the placenta and thus may affect the fetus. However, use of a small amount of marijuana does not appear to increase the risk of birth defects or to slow the growth of the fetus.

Marijuana does not cause behavioral problems in the newborn unless it is used heavily during pregnancy.

Opioids during pregnancy

Use of opioids during pregnancy increases the risk of complications during pregnancy, such as

Babies of heroin users are more likely to be small.

Drugs Used During Labor and Delivery

Drugs used to relieve pain during pregnancy Pain relief Labor is a series of rhythmic, progressive contractions of the uterus that gradually move the fetus through the lower part of the uterus (cervix) and birth canal (vagina) to the outside world... read more (such as local anesthetics and opioids) usually cross the placenta and can affect the newborn. For example, they can weaken the newborn's urge to breathe. Therefore, if these drugs are needed during labor, they are given in the smallest effective doses.

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