Pregnant Women  |  Carbon monoxide  |  Medication safety  |  Lead

Poisons and Pregnancy

The Bottom Line

There is a lot of information about avoiding drugs, alcohol, and tobacco while pregnant. There are some other poisons to be aware of if you're pregnant, including herbal medications, supplements, lead, and carbon monoxide.

The Full Story

True or false? An expectant mother needs to tell her doctor about all medicines she is taking, including herbal medicines, supplements, and over-the-counter medicines.

TRUE. There is a lot of information about avoiding drugs, alcohol, and tobacco while pregnant. Here are some other poisons to be aware of if you're pregnant.

  • Over-the-counter medicines, herbal medicines, and supplements: We often think only of prescription medicines when we provide a list to our health care providers.
    • Be sure to include any other medicines you are taking, whether or not they require a prescription.
    • Don't overlook any herbal or botanical medicines or teas you might take. Some of these have a long record of use during pregnancy; that's not the same as scientific evidence that they are safe. There is also the possibility of interactions with drugs needed during your pregnancy.
    • This applies to nutritional supplements, too; be sure your health care provider knows and approves of everything you are taking.
  • Carbon monoxide: This colorless, odorless, tasteless gas is dangerous for anyone, but most dangerous for developing fetuses. Carbon monoxide readily enters the fetal blood stream and deprives every organ of oxygen. It lasts much longer in fetal blood than in the mother's, thus the potential effects are magnified in the baby.
    • Every home should have carbon monoxide alarms outside of the sleeping areas. Professionals should regularly inspect fuel-burning appliances and adjust them as needed. Examples include gas furnaces, hot water heaters, stoves, and fireplaces; wood-burning stoves and fireplaces, along with chimneys and flues; and space heaters.
    • Pregnant women may need more aggressive treatment for carbon monoxide poisoning than others.
  • Lead: Lead poisoning in pregnant women can result in very high lead levels in their babies, both before and after birth. The infants will need aggressive treatment when they're born to lower their lead levels as soon as possible. Sources of lead for pregnant women often include home renovation projects, herbal or botanical drugs, supplements, and pica (eating non-food substances, such as soil, clay, paint chips, or pottery). Prevention is key, since lead stays in the body for decades.
    • If you know you had high lead levels earlier in your life, ask the doctor to check your lead level. Lead is stored in bone; as your body takes some calcium from your bone store for your baby, lead can be released into your bloodstream.
    • Houses built in or before 1978s were painted with lead-based paint. If lead is present, renovations must be carried out by a licensed contractor to control the release of lead into the air. Pregnant women, children, and perhaps other family members may need to relocate while the work is being done.
    • Take only supplements approved by your health care provider.
    • If you have pica, tell your health care provider so you can have your lead level tested if necessary.
  • Food-borne illness: You've read about concerns for mercury in fish and Listeria in soft cheeses, cold cuts, hot dogs, etc. Remember that garden-variety food poisoning from poor food handling practices can make you very ill. A lot of vomiting and diarrhea in a short time can lead to dehydration, which could be a problem for your pregnancy.
    • Be sure to wash your hands before handling or preparing food. Wash them again, along with your knives and cutting boards, after handling raw meat or seafood.
    • Keep foods at the correct temperature: hot foods hot, cold foods cold.
    • Eggs and meats should be cooked completely.

While you're preparing for your baby's birth, be sure to prepare for a poison emergency. Call 1-800-222-1222 to ask for phone stickers and a refrigerator magnet with Poison Control's 24-hour phone number. Program the number into your home and cell phones, too.

Rose Ann Gould Soloway, RN, BSN, MSEd, DABAT emerita
Clinical Toxicologist

For More Information

Using Dietary Supplements Wisely (National Center for Complementary and Alternative Medicine

Lead Screening During Pregnancy and Lactation (The American College of Obstetricians and Gynecologists)

Food Poisoning (The Poison Post®)


Agulnik Al, Maggion L, Wolng LF, Dwyer BK. Listeriosis and heart block in pregnancy. Obstet Gynecol. 2009;114(2):420-422.

Shamshirsaz AA, Yankowitz J, Rijhsinghani A, Greiner A, Holstein SA, Niebyl JR. Severe lead poisoning caused by use of health supplements presenting as acute abdominal pain during pregnancy. Obstet Gynecol. 2009;114(2):448-50.

Yildiz H, Aldemir E, Altuncu E, Celik M, Kavuncuoglu S. A rare cause of perinatal asphyxia: maternal carbon monoxide poisoning. Arch Gynecol Obstet. 2010;281:251-254. DOI 10.1007/s00404-009-1139-4


CALL 1-800-222-1222

Prevention Tips

If you're pregnant, be sure to:

  • Tell your health care provider about every medicine you take – prescription, non-prescription, herbal, botanical, and supplement.
  • Install carbon monoxide alarms outside every sleeping area of your home.
  • Ask if you should be screened for lead poisoning.
  • Follow the rules for preventing food poisoning.

This Really Happened

Case 1: A woman at the end of her second trimester of pregnancy went to her physician complaining of generalized acute abdominal pain. She was a vegetarian and had no known exposures to industrial toxins. She had had some loss of appetite and diarrhea 4 days earlier. She was released with a diagnosis of gastroenteritis. The patient presented again twice during the next 5 days with similar and then worsening complaints. She had no relief from taking Tylenol # 3®. An amniocentesis was normal. She had negative tests for hepatitis A, B, and C. She was hospitalized for 9 days. During that time her liver enzymes became elevated. She had a normal abdominal ultrasound and computed tomography scan (computers are used to scan and create cross-sectional images of internal organs).

While hospitalized, the patient revealed that she had been taking several Ayurvedic (a system of traditional Hindu medicine) preparations that she had obtained from a friend in India. One of them, Garbhpal ras, which means "protector of fetus," contained very high levels of lead. Blood and urine tests indicated possible lead poisoning. Her blood lead level was very elevated. The health supplements were then believed to be the source of the lead poisoning and she was advised to discontinue the supplements.

Ten days later, her blood lead level had decreased but was still very high. She underwent a 2-week course of succimer (a chelating agent that removes excess lead from the body). The patient delivered a boy at term, healthy with the exception of hypospadias (a condition in which the urethra is on the underside of the penis instead of at the tip; this is fairly common and can be surgically corrected). At the time of delivery the patient's lead level was still quite elevated and her newborn had an elevated blood lead level as well. He was also treated with succimer and was followed closely for 6 months and had normal developmental milestones. The mother received three more courses of succimer in the first 6 months after delivery.

Reference: Shamshirsaz AA, Yankowitz J, Rijhsinghani A, Greiner A, Holstein SA, Niebyl JR. Severe lead poisoning caused by use of health supplements presenting as acute abdominal pain during pregnancy. Obstet Gynecol. 2009;114(2):448–50.

Case 2: A 36-year-old woman presented to labor and delivery during her fifth pregnancy at 36 weeks of gestation with a 3-day history of chills, headache, and muscle aches and a 1-day history of diarrhea. She had a fever of 102 degrees Fahrenheit. Her heart rate was fast at 130-139 beats per minute (bpm). Fetal heart monitoring showed the baby's heart rate also to be fast at 200-200 bpm but was otherwise normal. The patient had emigrated from Mexico 2 years before and had had no other recent travel. She was admitted for observation and given medication to control her fever. Blood cultures were drawn. he next day she had no fever, both her and the fetal heart rates were normal, and she was discharged home.

Three days later, two of her blood cultures grew Listeria monocytogenes (a bacterium found in soil, water, contaminated meats and dairy products and raw milk). Cases of listeriosis are rare in the United States. Pregnant woman are more commonly affected than the general population. Infection usually results from eating contaminated foods including those made from unpasteurized milk (soft cheese), ready-to-eat delicatessen meats, and meat patés. The patient, when specifically questioned, confirmed eating unpasteurized soft Mexican cheese (queso fresco) before her symptoms began.

She was admitted to the hospital and treated with intravenous (IV) antibiotics. After 48-hours on antibiotics she no longer had a fever and had no other symptoms. Labor was induced. She had a normal spontaneous vaginal delivery of a healthy boy. The newborn showed no signs of infection. The placenta showed inflammation and abscesses.

The day after delivery, the patient had two episodes of loss of consciousness that were not witnessed by a medical provider. Upon immediate evaluation her physical examination and vital signs were unremarkable. A CT scan and MRI of the brain were normal as was a lumbar puncture (to study the spinal fluid). At 3 and 4 days after delivery she had a heart rate of 50-59 bpm. An electrocardiogram (ECG) on the 5th day after delivery showed a heart rate of 47 bpm and some heart conduction disturbances. On the 6th day after delivery her heart rate was 30-49 bpm and she had significant heart block (this occurs if heart's internal electrical signal is disrupted as it moves through the heart). She was transferred to the cardiac care unit. She was started on IV medication to raise her heart rate. Despite several such medications, her heart rate did not go over 50 bpm. A pacemaker was placed on the 14th day after delivery. She was on IV antibiotics for 16 days. Her subsequent blood cultures were negative. An ECG done 30 days after hospital discharge showed a properly functioning pacemaker. The fact that the heart was using the pacemaker indicated that her heart block had not yet resolved.

The heart block was believed to be a likely consequence of listeriosis. Listeria could have caused the heart block either by direct infection or an immune phenomenon. It is unlikely that the patient had pre-existing heart block since she did not initially present with a slow heart rhythm. It is believed that this is the first reported case of listeriosis in pregnancy complicated by heart block.

Reference: Agulnik Al, Maggion L, Wolng LF, Dwyer BK. Listeriosis and heart block in pregnancy. Obstet Gynecol. 2009;114(2):420-422.