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Pregnancy and Drugs

  1. Introduction
  2. How do I know which prescription drugs and over-the-counter medications are harmful?
  3. Which medications should I avoid?
  4. If a father takes drugs/medications, will this affect the baby?
  5. What kinds of illegal drugs are harmful to fetuses?
  6. Is smoking/tobacco use during pregnancy harmful?
  7. Can I drink alcohol if I’m pregnant?
  8. What does drinking during pregnancy do to a baby?
  9. How much caffeine can I drink while I’m pregnant?
  10. What kind of health problems can women and children who were exposed to DES (diethylstilbestrol) have?


A discussion of medications in pregnancy requires an understanding of how drugs are studied for efficacy (how well they work) and side effects in the general population. The best way to study any medication is to compare its effects to those of a placebo (sugar pill) in two identical groups of patients. This is called a randomized clinical trial. A large group of patients is randomly divided to create two equal groups. Randomly dividing them assures that any factors such as smoking, alcohol use, or coexisting medical problems is equally represented in each group, therefore canceling each other’s effects. One group is given the study medication; the other group is given a placebo that should have no effect. In a “double blind study,” both the patients being studied and the investigators are unaware of whether a patient is receiving the study medication or a placebo. This will prevent the investigator or patient from introducing his/her bias into the outcome. The best way of testing the effects of drugs on pregnancy would be to find two identical groups of pregnant women and give one group the drug to be studied, and give the other group a placebo (or sugar pill). Very few studies are done that way…

Very few studies involve pregnant patients. Most of the information we have comes from groups of women who were on a medication because of the belief that the benefits of the drug outweighed any potential risk-for example, drugs taken for seizure disorders, asthma, or mental illness. Fewer groups involve women who were undergoing treatment without the knowledge of being pregnant. Because there is no comparison group, the true effect of the medication is not exactly known. There is the possibility that the effect seen is secondary to the condition being treated, and not the medication given. For instance, it is believed that spinal cord defects are an effect of anti-seizure medication, but there is some evidence that women who suffer seizures are at increased risk of having an infant with a spinal cord defect despite the drugs used.

Many other confusing issues can arise that make studying drugs in pregnancy difficult. For one, there is a 2-3% random chance of a birth defect for every pregnancy. This makes it difficult to determine if the drug in question was the culprit or if the pregnancy had problems that resulted from random chance. As always, the best advice is to consult with your doctor and pharmacist about the potential risks versus benefits of any medication.

How do I know which prescription drugs and over-the-counter medications are harmful?

Drugs are given a pregnancy risk factor category of A through E by the Food and Drug Administration (and sometimes X) depending upon what has been learned through various animal and human studies done with the drug. If you are pregnant, or planning on becoming pregnant, check with your doctor or pharmacist before taking any drugs. Descriptions of pregnancy risk factor categories are listed below:

FDA Pregnancy Risk Factor Categories

CATEGORY A: Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is no evidence of a risk in later trimesters), and the possibility of fetal harm appears remote.

CATEGORY B: Either animal-reproduction studies have not demonstrated a fetal risk, but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of a risk in later trimesters).

CATEGORY C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other), and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

CATEGORY D: There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).

CATEGORY E: Studies in animals or human beings have demonstrated fetal abnormalities, or there is evidence of fetal risk based on human experience, or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Which medications should I avoid?

There are some medications that we know cause harm when used in pregnancy and should be avoided. Some examples of these medications are:

Aspirin – Aspirin is a Category C drug. Studies of aspirin during pregnancy have been difficult to perform because many patients fail to report taking aspirin during their pregnancy because they forgot they had used it and it is a commonly used medication. Nevertheless, there have been many associated side effects to mothers and babies while taking full-dose aspirin during pregnancy. This is not the same as taking a baby aspirin, which is recommended for some women who are at high risk of developing pregnancy-associated complications. It is especially important to avoid aspirin during the last 3 months of pregnancy, because it can cause problems in the fetus or complications during delivery. Tylenol taken in moderation can be used as a substitute.

Accutane – Accutane, or isotretinoin, is a powerful prescription drug that can clear severe acne. If taken during pregnancy, it can cause birth defects (such as heart defects, small jaw, cleft palate, and skull and facial disfigurements) in about 1 of every 4 fetuses. It can also cause miscarriages. Currently, doctors will not prescribe Accutane to pregnant women, women who are trying to become pregnant, or women who are not taking effective contraception and are at risk of pregnancy. Before being permitted to take Accutane, a woman of child-bearing age must sign a consent form stating that she has been fully informed of the drug’s side effects.

Tegison – Tegison, or Etretinate, is a prescription drug to treat psoriasis. Pregnant women are forbidden to use this drug. Since it is not known how long pregnancy should be avoided after treatment stops, a woman must plan on never having children if she is treated with Tegison. Women of childbearing age must have a pregnancy test within 2 weeks before beginning treatment to make sure they are not pregnant. Contraception must be continued during treatment and for as long as you are able to become pregnant after treatment is stopped. Be sure to discuss this information with your doctor.

Thalidomide – Thalidomide is a sedative drug that was introduced in 1958 and widely used to treat the morning sickness of pregnancy. It was later found to cause miscarriage and severe birth defects, such as stunted, shortened limbs and other deformities of the arms and legs, cleft palate, deafness, and blindness. While it is not approved for general sale in the United States anymore, the FDA still allows Thalidomide to be used in certain studies for the treatment of other diseases and conditions, such as skin sores caused by lupus and leprosy. Thalidomide is also used to treat problems that are caused by other diseases, such as severe mouth ulcers and graft-versus-host disease (a kind of transplant rejection). Women of childbearing age should not participate in studies involving Thalidomide unless they are currently practicing abstinence (not having sexual intercourse) or a highly reliable form of birth control.

If a father takes drugs/medications, will this affect the baby?

Little is known about the effect of drugs and medications on the baby when the father takes them, but it is believed to be little or none. The medications taken by the father are likely to have an “all or nothing” effect on his sperm. In other words, the only effect would probably be lower sperm production and infertility. There are few drugs that will affect sperm production in this way. However, second-hand smoke by a father affects the health of fetuses and newborns. New studies show that if a woman’s partner smokes near her during her pregnancy, there are added risks. She has a greater chance of having a baby with a low birth weight and other health problems.

What kinds of illegal drugs are harmful to fetuses?

All illegal drugs can be harmful to fetuses, and should be avoided during pregnancy. Some of the most common illegal drugs and their side effects are listed below:

Marijuana – The research studies on marijuana effects on fetal development during pregnancy are based on animal studies and the results are conflicting. Some studies have shown that infants exposed to marijuana will have fine tremors, and irritability. What is known is that marijuana does cross into the fetal circulation and reduces the amount of oxygen available to the growing fetus.

Crack/Cocaine – Crack and cocaine have some of the most dangerous side effects for both the mother and the baby. Some complications the mother may experience include cardiovascular problems, pulmonary disease, liver damage, seizures and death. They are also at increased risk for preterm labor and delivery, and have babies with a lower birth weight. As blood pressure rises, the placenta can separate from the uterus causing fetal death and serious bleeding problems in the mother. Other effects of cocaine use include birth defects and brain damage in the baby.

Heroin – Heroin users are at high risk for malnutrition, anemia, pre-eclampsia (high blood pressure occurring in pregnancy), placental abnormalities, pre-term labor, and premature rupture of membranes. The infant will often be born addicted to heroin, and will go through withdrawal following birth. These infants are irritable, difficult to comfort, have a shrill high cry, and may have seizures.

Often, there are associated problems with alcohol and drug use, such as poor nutrition and infections, which harm the pregnancy. If someone you know is using drugs in pregnancy, she should be encouraged to seek help for her health and the health of their baby.

Is smoking/tobacco use during pregnancy harmful?

A woman who smokes takes in poisons such as nicotine and carbon monoxide (the same gas that comes out of a car’s exhaust pipe). These poisons get into the placenta, which is the tissue that connects the mother and the baby before it is born. These poisons keep a fetus from getting the food and oxygen it needs to grow. Smoking is associated with pregnancy complications, early menopause, and reduced fertility. Women who smoke during pregnancy increase the risk of miscarriage, stillbirth, premature delivery, low birth weight babies, ectopic pregnancies (implanting of the embryo outside of the uterus), and infant death. Tobacco use during pregnancy slows the growth of a fetus, especially in women who smoke more than 1 pack per day. Infants are also more likely to die from Sudden Infant Death Syndrome (crib-death) if their mothers smoke. Second-hand smoke from other people also affects a pregnant woman and her fetus. For more information on smoking, click here.

Can I drink alcohol if I’m pregnant?

You should not drink alcohol while you are pregnant. If you plan to get pregnant, do not drink. If you drank alcohol before you knew you were pregnant, stop now. When you drink alcohol, so does your baby. Drinking any type of alcohol during pregnancy can hurt your baby. This includes beer, wine, wine coolers, liquor and mixed drinks. Although not all babies are affected, there is no established safe amount that can be taken in pregnancy. Alcohol can hurt a baby even if you are only 1 or 2 months pregnant.

What does drinking during pregnancy do to a baby?

Drinking can cause a variety of physical and behavioral problems that are not curable and will not go away. Children born with the most serious problems caused by alcohol have fetal alcohol syndrome (FAS). Children with FAS may:

  • Be born premature, small, and underweight
  • Have problems eating and sleeping
  • Have problems seeing and hearing
  • Have problems paying attention, following directions, and learning in school
  • Need special teachers and schools
  • Have trouble getting along with others and controlling their behaviors
  • Need expensive and serious medical care all their lives

How much caffeine can I drink while I’m pregnant?

The effects of caffeine on a fetus are still not clear. One study found that pregnant women consuming moderate to heavy amounts (150mg/day or one and a half cups of coffee) are more likely to experience late first and second trimester spontaneous abortions (miscarriage) compared to women who consume less than 150mg daily. Consuming 300mg (3 cups of coffee) or more is considered heavy usage, and those women are 50% more likely to spontaneously abort. Caffeine may cause spontaneous abortion by altering the blood flow to the placenta. Another side effect of decreased blood flow is that the baby does not receive all of the nourishment it needs. Malnourishment can restrict growth and lower birth weight. Caffeine consumption of 300mg or more increases the risk of having a low birth-weight baby, and may cause a reduction in head circumference as well. Other equally well designed studies have shown no influence of caffeine on pregnancy.

1 cup of coffee = about 100mg of caffeine
1 cup of tea = about 40mg of caffeine
1 soda/pop = about 40mg of caffeine (this will vary depending on the type of soda)

What kind of health problems can women and children who were exposed to DES have?

DES (diethylstilbestrol) was used to prevent miscarriages from 1938 to 1971. In 1971, use of DES during pregnancy was related to an increase in the number of clear cell carcinomas of the vagina of female babies. The peak incidence of vaginal cancer in the child was at age 19. Use of the drug was also related to deformities in the development of the uterus that can increase the chance of miscarriage. The women exposed to DES in the uterus may have a problem with the cervix (opening to the uterus) dilating and opening prematurely in the second trimester of pregnancy. DES has not been used in pregnant women since 1971. We do not know whether the women who were exposed while in their mother’s wombs are at risk for development of other cancers.

It has been estimated that 5 to 10 million people were exposed to DES during pregnancy. Many of these people are not aware that they were exposed. A woman who was pregnant between 1938 and 1971 and had problems or a history of problems during pregnancy may have been given DES or a similar drug. If you think you or your mother used a hormone such as DES during pregnancy, you should try to contact the attending physician or the hospital where the delivery took place to ask whether there is any record that you or your mother received DES. If any pills were taken during pregnancy, records should be checked to determine the name of the drug. Mothers and children have a right to this information.

Women who took DES: Women who took DES are advised to pay particular attention to their breast care, because they may have a small increase in their risk of breast cancer. Mothers are advised to tell their DES-exposed sons and daughters about their exposure, even if these children have not had health problems. They need to know about DES so they can get the health care they need.

DES Sons: Men who were exposed to DES before birth (while their mother was pregnant) are at increased risk for non-cancerous cysts on the back of the testicles (on the epididymis) and for underdeveloped testicles. DES sons should practice testicular self-examinations regularly. There has been little research on the effects of DES exposure in DES sons, but new studies are in progress. To protect your health, find out if you were exposed, and stay informed of new research findings.

DES Daughters: Women who were exposed to DES before birth need regular screening exams for a rare form of vaginal cancer (early detection saves lives). This exam is somewhat different from the one for non-exposed women. It should begin at puberty and continue throughout their lives. All DES daughters need special care beginning in the first weeks of pregnancy, even if they have already had children. With proper care, most DES daughters can have successful pregnancies.

In general, a woman should consult with her physician before starting any new medications during pregnancy. This includes over the counter medications, vitamins or supplements. Women who are currently taking medication should discuss this with their healthcare provider before becoming pregnant. This will assure the best possible outcome for your pregnancy.

For more information:

Go to the Pregnancy health topic.