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:
They can act directly on the fetus, causing damage, abnormal development (leading to birth defects Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life. The cause of many birth... read more ), or death.
They can alter the function of the placenta, usually by causing blood vessels to narrow (constrict) and thus reducing the supply of oxygen and nutrients to the fetus from the mother. Sometimes the result is a baby that is underweight and underdeveloped.
They can cause the muscles of the uterus to contract forcefully, indirectly injuring the fetus by reducing its blood supply or triggering preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more and delivery.
They can also affect the fetus indirectly. For example, drugs that lower the mother's blood pressure may reduce blood flow to the placenta and thus reduce the supply of oxygen and nutrients to the fetus.
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 a drug affects a fetus depends on
The fetus's stage of development
The strength and dose of the drug
The permeability of the placenta (how easily substances pass through it)
The genetic make-up Genetic Makeup and Response to Drugs Differences in genetic (inherited) makeup among individuals affect what the body does to a drug and what the drug does to the body. The study of genetic differences in the response to drugs... read more of the mother, which affects how much of the drug is active and available
Other factors related to the mother (for example, if the mother is vomiting, she may not absorb as much of a drug, so the fetus is exposed to less of the drug)
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.
Vaccines During Pregnancy
Immunization Overview of Immunization Immunization enables the body to better defend itself against diseases caused by certain bacteria or viruses. Immunity (the ability of the body to defend itself against diseases caused by certain... read more is as effective in women who are pregnant as in those who are not.
Vaccines Overview of Immunization Immunization enables the body to better defend itself against diseases caused by certain bacteria or viruses. Immunity (the ability of the body to defend itself against diseases caused by certain... read more made with a live virus (such as the rubella vaccine Measles, Mumps, and Rubella Vaccine The measles, mumps, and rubella (MMR) vaccine is a combination vaccine that helps protect against these three serious viral infections. The vaccine contains live but weakened measles, mumps... read more and varicella vaccine Varicella Vaccine The varicella vaccine helps protect against chickenpox (varicella), a very contagious infection caused by the varicella-zoster virus. It causes an itchy rash that looks like small blisters with... read more ) are not given to women who are or might be pregnant.
Other vaccines (such as those for cholera Vaccines Cholera is a serious infection of the intestine that is caused by the gram-negative bacteria Vibrio cholerae and that causes severe diarrhea, which can be fatal without treatment. People... read more , hepatitis A Hepatitis A Vaccine The hepatitis A vaccine helps protect against hepatitis A. Typically, hepatitis A is less serious than hepatitis B. Hepatitis A often causes no symptoms, although it can cause fever, nausea... read more , hepatitis B Hepatitis A Vaccine The hepatitis A vaccine helps protect against hepatitis A. Typically, hepatitis A is less serious than hepatitis B. Hepatitis A often causes no symptoms, although it can cause fever, nausea... read more , plague, rabies Prevention Rabies is a viral infection of the brain that is transmitted by animals and that causes inflammation of the brain and spinal cord. Once the virus reaches the spinal cord and brain, rabies is... read more , and typhoid Vaccination Typhoid fever is caused by certain types of the gram-negative bacteria Salmonella. It typically causes a high fever and abdominal pain. Typhoid fever can be spread by consuming food or... read more 
) are given to pregnant women only if they are at substantial risk of developing that particular infection and if the risk of side effects from the vaccine is low.
However, all pregnant women who are in the 2nd or 3rd trimester during the influenza (flu) season should be given the influenza vaccine Influenza Vaccine The influenza virus vaccine helps protect against influenza. Two types of influenza virus, type A and type B, regularly cause seasonal epidemics of influenza in the United States. There are... read more .
All pregnant women should be given the tetanus-diphtheria-pertussis (Tdap) vaccine Diphtheria-Tetanus-Pertussis Vaccine The diphtheria, tetanus, and pertussis vaccine is a combination vaccine that protects against these three diseases: Diphtheria usually causes inflammation of the throat and mucous membranes... read more between 27 and 36 weeks of each pregnancy. This vaccine protects against pertussis Pertussis Pertussis is a highly contagious infection caused by the gram-negative bacteria Bordetella pertussis, which results in fits of coughing that usually end in a prolonged, high-pitched,... read more (whooping cough).
The CDC recommends COVID-19 vaccination COVID-19 Vaccine Coronavirus disease 2019 (COVID-19) vaccines provide protection against COVID-19. COVID-19 is the disease caused by infection with the SARS-CoV-2 virus. There are multiple COVID-19 vaccines... read more for all people 5 years and older, including people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future. Evidence about the safety and effectiveness of COVID-19 vaccination during pregnancy has been growing. These data suggest that the benefits of receiving a COVID-19 vaccine outweigh any known or potential risks of vaccination during pregnancy. (See also CDC: COVID-19 Vaccines While Pregnant or Breastfeeding.)
Drugs Used to Treat Heart and Blood Vessel Disorders During Pregnancy
Drugs to lower high blood pressure (antihypertensives Drug therapy High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more 
) may be needed by pregnant women who have had high blood pressure before pregnancy or who develop it during pregnancy. Either type of high blood pressure increases the risk of problems for the woman (such as preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more ) and for the fetus (see page High Blood Pressure During Pregnancy High Blood Pressure During Pregnancy High blood pressure (hypertension) during pregnancy is classified as one of the following: Chronic hypertension: Blood pressure was high before the pregnancy. Gestational hypertension: Blood... read more ). However, antihypertensives can markedly reduce blood flow to the placenta if they lower blood pressure too rapidly in pregnant women. So pregnant women who have to take these drugs are closely monitored.
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.
Digoxin, used to treat heart failure Heart Failure and some abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more 
, readily crosses the placenta. But at the usual doses, digoxin typically has little effect on the baby before or after birth.
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 loss of interest in usual activities during the first few weeks or months after delivery. Women who have had depression previously are... 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
Although cigarette smoking Smoking Smoking tobacco is harmful to almost every organ in the body. Smoking increases the risk of heart attack, lung cancer, chronic obstructive pulmonary disease (COPD), and other disorders. Nicotine... read more harms both pregnant women and their fetus, only about 20% of women who smoke are able to quit 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:
Premature detachment of the placenta (placental abruption Placental Abruption Placental abruption is the premature detachment of a normally positioned placenta from the wall of the uterus, usually after 20 weeks of pregnancy. Women may have vaginal bleeding and/or severe... read more , or abruptio placentae)
Premature rupture of the membranes Prelabor Rupture of the Membranes (PROM) Prelabor rupture of the membranes is the leaking of amniotic fluid from around the fetus at any time before labor starts. After the membranes rupture, labor often soon follows. If labor does... read more (containing the fetus)
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.
The risk of miscarriage Miscarriage A miscarriage is the loss of a fetus due to natural causes before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect)... read more almost doubles for women who drink alcohol in any form during pregnancy, especially if they drink heavily.
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:
A small head (microcephaly Microcephaly Microcephaly is an abnormally small head. Often the head is small because the brain is small and abnormally developed. Microcephaly can be caused by many disorders including genetic abnormalities... read more
), probably caused by inadequate growth of the brainIntellectual disability
Abnormal behavioral development
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 evidence suggests that drinking more than seven cups of coffee a day may increase the risk of having a stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Pregnancy complications are problems that occur only during pregnancy. They may affect the woman, the fetus, or both and may occur... read more , premature birth Premature Newborn A premature newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, premature newborns have underdeveloped organs, which may not be ready to function outside... read more , low-birth-weight baby 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 , or miscarriage Miscarriage A miscarriage is the loss of a fetus due to natural causes before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect)... read more .
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.
Pregnant women with phenylketonuria Phenylketonuria (PKU) Phenylketonuria is a disorder of amino acid metabolism that occurs in infants born without the ability to normally break down an amino acid called phenylalanine. Phenylalanine, which is toxic... read more , an unusual disorder, should not consume any aspartame.
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 
(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
Use of amphetamines Amphetamines Amphetamines are stimulant drugs that are used to treat certain medical conditions, but are also subject to abuse. Amphetamines increase alertness, enhance physical performance, and produce... read more during pregnancy may result in birth defects, especially of the heart, and possibly inadequate growth before birth.
Bath salts during pregnancy
Bath salts refers to a group of designer drugs made from various substances that resemble amphetamine. More and more pregnant women are using these drugs.
The drugs may cause the blood vessels in the fetus to narrow, reducing the amount oxygen the fetus gets.
Also, these drugs increase the risk of the following:
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:
Premature detachment of the placenta (placental abruption Placental Abruption Placental abruption is the premature detachment of a normally positioned placenta from the wall of the uterus, usually after 20 weeks of pregnancy. Women may have vaginal bleeding and/or severe... read more , or abruptio placentae)
Birth defects Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life. The cause of many birth... read more (including brain and spinal cord, urinary tract, and bone defects)
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
Hallucinogens Hallucinogens Hallucinogens are a class of drugs that cause profound distortions in people's perceptions. Hallucinogens distort and intensify sensations, but the actual effects are variable and highly... read more may, depending on the drug, increase the risk of the following:
Miscarriage
Premature labor and delivery
Hallucinogens include methylenedioxymethamphetamine (MDMA, or Ecstasy), rohypnol, ketamine, methamphetamine, and LSD (lysergic acid diethylamide).
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)... 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
Opioids Opioids Opioids are a class of drugs derived from the opium poppy (including synthetic variations) that are pain relievers with a high potential for misuse. Opioids are used to relieve pain, but they... read more are used to relieve pain, but they also cause an exaggerated sense of well-being, and if used too much, they can cause dependence and addiction.
Opioids Opioids Opioids are a class of drugs derived from the opium poppy (including synthetic variations) that are pain relievers with a high potential for misuse. Opioids are used to relieve pain, but they... read more , such as heroin, methadone, and morphine, readily cross the placenta. Consequently, the fetus may become addicted to them and may have withdrawal symptoms Withdrawal symptoms Opioids are a class of drugs derived from the opium poppy (including synthetic variations) that are pain relievers with a high potential for misuse. Opioids are used to relieve pain, but they... read more 6 hours to 8 days after birth. However, use of opioids rarely results in birth defects.
Use of opioids during pregnancy increases the risk of complications during pregnancy, such as
Miscarriage
Preterm delivery
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.
Drugs Mentioned In This Article
| Generic Name | Select Brand Names |
|---|---|
thalidomide |
THALOMID |
meclizine |
No US brand name |
heparin |
No US brand name |
warfarin |
COUMADIN |
isotretinoin |
ABSORICA |
spironolactone |
ALDACTONE |
digoxin |
LANOXIN |
paroxetine |
PAXIL |
zidovudine |
RETROVIR |
ritonavir |
NORVIR |
remdesivir |
VEKLURY |
zanamivir |
RELENZA |
oseltamivir |
TAMIFLU |
acyclovir |
ZOVIRAX |
nicotine |
COMMIT, NICORETTE, NICOTROL |
amphetamine |
ADDERALL XR 10 |
ketamine |
KETALAR |
methamphetamine |
DESOXYN |
methadone |
DOLOPHINE |
morphine |
DURAMORPH PF, MS CONTIN |
