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The womb acts as a wonderfully protective cushion between the fetus and the jolts and bumps of the outside world. On the inside, though, the placenta simply cannot shield the womb from all of the man-made chemicals that have, according to the U.S. Centers for Disease Control, collected in our bodies. You can, however, take simple steps to reduce the risk to your offspring by paying special attention to what you eat, drink and breathe.

You probably already know to avoid alcohol, cigarette smoke, caffeine and kitty litter. Unfortunately, prenatal exposures to other common contaminants can affect the fetus during critical windows when vital systems are developing, says pediatrician Philip Landrigan, M.D., director of the Center for Children's Health and the Environment (CCHE) at the Mount Sinai School of Medicine in New York City. Below are 10 kinds of toxins capable of crossing the placenta and how to avoid them.

1. Trim consumption of animal fats
When you're pregnant, it's more important than ever to choose lean cuts of meat, trim away fat and opt for fat-free dairy products. Here's why: Some toxins linked to prenatal nervous system and hormonal damage are stored in fatty tissue. These include polychlorinated biphenyls (PCBs), which pose risks of reduced intelligence to the developing fetus; brominated fire retardants; dioxins and other pollutants that persist in our air and water.

2. Put a stop to insecticides in your home and office
Organophosphates are a family of insecticides that attack the nervous system. In two New York City studies conducted last year, babies of women who had been most exposed to two organophosphates, chlorpyrifos (Dursban and Lorsban) and diazinon (Spectracide), had significantly lower birth weights. Fortunately, these insecticides were phased out of residential and school use by the EPA in 2001-03. However, other organophosphates are still in circulation, as are similar compounds called pyrethroids. Pesticides also release inhalable volatile organic compounds (see below).

What to do instead? Researchers at the Columbia Center for Children's Environmental Health (CCCEH) recommend that pregnant women switch to sticky traps and other bait stations, "which are safer, last longer and are more effective," while keeping surfaces clean of food residue, removing trash and treating cracks with boric acid, classified by the EPA as of low toxicity, then sealing with caulk. (Keep boric acid and baits out of the reach of children and pets.)

3. Select foods to minimize pesticide residues
Chlorpyrifos and diazinon (see above), along with many related toxic pesticides, are still used widely on food crops. Prioritize your grocery list to allow for the purchase of the following organic fruits and vegetables that, when conventionally grown, tend to harbor the most pesticide residue: apples, bell peppers, celery, nectarines, peaches, pears, potatoes, spinach, strawberries and peppers.

4. Pass on high-mercury fish
Mercury is a potent neurotoxin that can harm a developing fetus. Say "no" to high-mercury fish such as fresh tuna, canned albacore, wild bass, swordfish and tilefish. (One meal of moderate-mercury fish, such as canned light tuna, can be eaten once a month.) Eat up: low-mercury "yes" fish such as sardines, wild salmon and farmed striped bass.

5. Let Old Paint Lie
Since lead has been banned from gasoline (in 1996) and paint (in 1978), most exposures now come from old lead-based paint. This heavy metal, which can also contaminate water and soil, can interfere with nearly every aspect of fetal development, causing brain and kidney damage, according to the CCHE. If your old house has lead paint in good condition, cover it with fresh paint rather than removing it, which releases lead dust into the air. To test paint for lead, see www.epa.gov/lead or call the EPA's lead hot line at 800-426-4791.