Toxins and Pregnancy

You're finally pregnant – and the world seems fraught with dangers. Here's a guide to help you navigate through the legitimate concerns and the baseless worries.

Medically Reviewed by Louise Chang, MD on October 01, 2008
9 min read

When you're expecting a baby, how vigilant do you need to be about possible toxins? Sure, you'll want to steer clear of smokers, the cat's litter box, and margaritas. But what about the sushi bar, nail polish, and bottled water?

With new alarms sounded almost daily, it's a challenge to know what to do.

WebMD turned to the experts for advice. Unfortunately, the territory is not clearly charted. Besides the known risks, there lurks a vast gray area in which the research is inconclusive. According to the March of Dimes web site, the cause of about 70% of birth defects is unknown. And most known defects are due to genetic or other unpreventable causes -- not to mom's exposure to toxic chemicals, foods, drugs, or infections.

So is there any way to lower the risk? The following information should help you separate the facts from the likely fiction.

Substances that can cause birth defects are called "teratogens." Exposure to them does not automatically put your fetus at risk. The level and length of time of exposure, as well as the stage of the pregnancy at time of exposure, can come into play. According to the educational bulletin on teratology published by the American College of Obstetrics and Gynecology (ACOG), the following are among the known causes of birth defects:


  • Cytomegalovirus
  • Rubella
  • Syphilis
  • Toxoplasmosis
  • Varicella

The thalidomide scare of the 1960s is legendary. Yet in terms of risk and impact, it pales in comparison to isotretinoin, best-known by the brand name Accutane, according to Lynn Martinez, Utah State Health Department coordinator of the Pregnancy Riskline in Salt Lake City.

"It's an amazing drug approved for severe nodular or cystic acne, but it's estimated that in the U.S., 90% of prescriptions are off label. Someone gets an outbreak of pimples and wants Accutane," she says.

Martinez tells WebMD that if a woman takes the drug during pregnancy, there is a 30% to 35% risk for major birth defects, including complete absence of the thymus gland; serious, often lethal, heart defects; absence of the inner and outer ears; and severe, possibly lethal, hydrocephalus - a buildup of excess fluid in the brain. Furthermore, of the 65% of babies born without structural malformations, 50% are profoundly intellectually disabled.

"It's interesting to me that by comparison, Accutane's risk is much higher than thalidomide's -- which carries a 20% risk -- and its harm to the child is far worse," she says.

Black-box warnings on prescription labels indicate the highest level of risk determined by the FDA.

But the recent black-box labeling of the antidepressant Paxil causes confusion for pregnant women, says Martinez.

"Two recent published studies show a slight risk for heart defects with Paxil, a selective serotonin reuptake inhibitor, or SSRI. But four large cohort studies that followed women through pregnancy and followed the children until they were 9 years old don't show higher risk.

"We're letting people know about the studies, but we're withholding judgment," she says.

Martinez explains that a problem arises when depressed women are taken off Paxil and other SSRIs, which have been associated with problems of neonatal adaptation. "Some women are then given tricyclic antidepressants, which carry a much higher risk for far more significant neonatal withdrawal. Or they're taken off antidepressants altogether.

"In the cohort studies, the children in a control group of depressed women taking no antidepressants were more likely to have delayed developmental milestones and more difficulties in school than the children whose mothers took antidepressants," says Martinez.

The U.S. Environmental Protection Agency (EPA) estimates that 630,000 babies in the U.S. are born annually with high levels of mercury, which can lead to neurological, cognitive, and developmental problems. Most often, the mothers were exposed to methylmercury from eating contaminated fish. Nursing mothers can also pass mercury to their infants.

Because mercury lingers in the blood, all women of childbearing age should follow these guidelines issued jointly by the EPA and FDA:

  • Do not eat shark, swordfish, king mackerel, or tilefish.
  • Eat no more than 12 ounces (two average servings) a week of fish with lower levels of mercury, like shrimp, canned light tuna, salmon, pollock, and catfish.
  • Eat no more than 6 ounces a week of albacore (fancy, white) tuna.
  • Check fish advisories before eating locally caught fish.

Don't exclude fish and shellfish from your diet, however, says Lola O'Rourke, spokeswoman for the American Dietetic Association. They are sources of high-quality protein and omega-3 fatty acids, and are low in saturated fat. She advises varying the types of "safe" fish you consume to lower any risk of contamination.

O'Rourke offers these additional food tips:

  • Avoid raw sprouts and unpasteurized juices, milk products, and soft cheeses. They are potential sources of harmful bacteria such as salmonella, E. coli, listeria, and shigella.

  • Avoid raw or undercooked meat, fish, poultry, and eggs.

  • Avoid cold cuts and deli meats unless heated until steaming.

  • All leftovers should be heated until steaming.

  • Wash hands often. Wash produce well. Keep raw meats separate from other foods.

  • Refrigerated foods should not be left out more than two hours. Set the refrigerator between 35 and 40 degrees.

Also, "The more whole food and the fewer processed foods, the better," O'Rourke tells WebMD. "You'll get fewer preservatives, trans fats, and additives.

"Also, consult your doctor about vitamins. There's such a thing as getting too much," she says.

According to ACOG, there is "limited evidence of varying degrees to document teratogenicity" for a number of agents -- some of which may surprise you.

Linda R. Chambliss, MD, MPH, spokeswoman at ACOG, explains that the lack of conclusive data on such agents is due to research constraints.

"The best research requires randomized studies in which you have a group of people exposed to a substance and a control group that's not exposed. Researchers are loathe to put pregnant women into randomized studies [exposing some to potential toxins], so they rely on animal studies or on women reporting what they were exposed to during pregnancy," she says.

Chambliss, a professor of obstetrics and gynecology at St. Louis School of Medicine in Missouri, talks to WebMD about her advice on some of the most common "gray area" substances:

"You do not want [to take] aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), such as Advil or Motrin. They can affect platelet count and bleeding time, and have been associated with fetal defects. I would advise a pregnant woman to avoid these unless they're prescribed by a physician." Acetaminophen, or Tylenol, should be taken instead of aspirin, Advil, or Motrin for fever, headache, minor aches, and pains.

"There's little data on newer antihistamines. The older ones work by causing vasoconstriction [constriction of blood vessels], so there's some concern about using them in the first trimester." Examples of antihistamines include Claritin, Zyrtec, Allegra, and Benadryl.

"not a lot of information".

"ACOG and the American Academy of Pediatrics say that moderate use, about a couple of cups per day, does not increase reproductive risk. Many people who use caffeine also smoke and drink alcohol, so it's hard to tease out caffeine. Is it the smoking, caffeine, alcohol? Or do they work synergistically? It's not clear."

"Fertilizers might pose a problem for agricultural workers, but for occasional residential use, you don't have to leave your house when your lawn gets fertilized. Working in an office where you use Wite-Out or permanent markers is not a concern, but tell your physician about occupational exposures in industrial or agricultural environments. A lot of obstetricians don't think to ask about occupational exposure."

"If a woman continued taking oral contraceptives because she didn't know she was pregnant, I would tell her to stop. There have been some problems in terms of birth defects. The doctor will take a look at possible interactions and perhaps use an ultrasound to look at the fetus. What has been reported is a less than 1% risk of masculinization of the female fetus."

"If you have your house sprayed for bugs routinely, I'd be concerned; but if it's a one-time exposure, use common sense. Pesticides have real risks, but most of the data involves agricultural workers."

Journalists Deirdre Dolan and Alexandra Zissu conducted exhaustive research because they wanted their pregnancies to be the healthiest possible. They recently published that information in a book, The Complete Organic Pregnancy, that looked at "what you need to know -- from the nail polish you wear to the bed you sleep in to the water you drink."

Martinez has not read the book. But, she notes, "There's so much information out there that serious messages -- like the risk of Accutane -- get lost."

She and O'Rourke commented on a few of the risks cited in the book:

"Don't worry about getting your nails done," says Martinez. "Regarding chemical exposure, we worry about chronic or acute poisoning. For example, if you worked in a nail salon and had severe headaches day after day, it would indicate there's too much toxin in the bloodstream and you would be at increased risk for miscarriage."

OK, says Martinez.

OK, says Martinez.

when you pump: "Don't sniff them to get high," advises Martinez.

commonly treated with PBDE fire retardant chemicals: OK, says Martinez.

interior: OK, says Martinez.

maternity clothes: "They're OK," says Martinez. "A concern would be for someone working in a mom-and-pop shop that doesn't meet OSHA standards."

"Once opened, don't keep bottled water longer than a week," says O'Rourke. "I wouldn't re-use them. That has to do with bacterial contamination, not plastic leaching into the water. Recycle them."

"If you're in a public water system, it should be safe," says O'Rourke. "If you're on a well, presumably you have it tested regularly."

on food: "I wouldn't heat things up with it," says O'Rourke. "We don't know about how it breaks down."

"Used properly, at low temperatures with non-abrasive utensils, it's fine," says O'Rourke.

"Levels of pesticides in conventionally produced fruits and vegetables are considered to be safe," says O'Rourke. "All produce, including organically grown, should be washed."

Women who are pregnant are at high risk for complications from influenza, according to the CDC. It's safe to get a flu shot at any time during your pregnancy, says Martinez. "Pregnant women are especially at risk of morbidity during the second and third trimesters."

Also, make sure you're up-to-date on any needed vaccinationsbefore you become pregnant. Rubella, or German measles, for instance, poses a serious risk to fetuses in the first trimester of pregnancy.

Utah's Pregnancy Riskline is one of more than 30 North American services belonging to the Organization of Teratology Information Services. Detailed fact sheets, and contact information for state and regional resources can be found on their web site.

Also, the March of Dimes web site is a good source of information.

"Use caution with any exposure in the first trimester and moderation throughout the second or third," advises Chambliss. "Communicate clearly to your physician anything you're taking, including prescriptions, home remedies, [over-the-counter] medications, vitamins, and alternative medicines. Also mention exposure to occupational chemicals."

If you're in doubt about a particular drug or substance, ask the doctor. Ideally, you should talk to your doc about the medications you're taking and other concerns before becoming pregnant so you can make any necessary changes. There are dietary supplements - like folic acid - that are best started before pregnancy. And some toxins can linger in the body even if you end your exposure.