During Pregnancy

Choosing organic during pregnancy depends on only one key factor: what you crave, says registered dietitian Bridget Swinney, author of the books Eating Expectantly, Baby Bites, and Healthy Food for Healthy Kids. She recommends that you keep a journal of what you eat over a period of about two weeks, then buy organic versions of the foods that top your list.

If you're a beef-eater, Dr. Greene suggests choosing grass-fed, organically raised cattle. It's leaner and healthier, and can have up to five times the amount of brain-building omega-3 fatty acids as regular beef. Though the cost of organic meat can be double that of regular, try treating it like a side dish and opt for smaller servings.

Also consider another source of organic protein that may be less expensive than beef: soy. But remember that despite its close association to healthy living, soy doesn't always equate organic. Eighty percent of the soybean crops grown today are genetically modified, which means the genetic code of the food has been altered in a lab to make it more weed- or bug-resistant. Dr. Greene says the problem is that no one really knows yet what impact genetically modified foods will have on our health and our farmlands. So make sure to check the packaging, and don't mistake an "all-natural" label on soy -- or any other product -- as a synonym for organic.

Finally, think about switching to organic milk. Pregnant women need to consume a lot of calcium, as much as 1,500 milligrams a day. The reason is that during pregnancy, the calcium transfer from mother to baby reaches 270 milligrams a day. For that reason, milk is one of Dr. Greene's top organic picks. And though the FDA maintains that all types of milk are equally safe, choosing organic means saying no to a whole chemical system of agriculture.

New Moms

You might expect the nutrition advice for new moms to be the same as during pregnancy, and certainly the above suggestions still hold true. But there are a few more recommendations to keep in mind.

If you're breastfeeding, Breast milk provides your baby's source of DHA, an omega-3 fatty acid that's important to brain and vision development, so eating DHA-rich foods like salmon is important. Experts recommend you shoot for 300 to 500 milligrams of DHA a day. A serving of salmon (a six to eight ounce filet) packs that and more.

However, the debate over organic seafood is ongoing. Dr. Greene notes that the USDA has no classification yet for organic seafood. According to the FDA, pregnant and nursing women can safely eat 12 ounces, or two servings, a week of wild salmon, tilapia, shrimp, catfish, and cod. If you want to buy these items organic, look for the Marine Stewardship Council logo on the label, which certifies where the fish came from (farmed or wild).

Nursing moms should also consume lots of vitamin A. It's passed in the breast milk from mother to baby, and if you're not careful, mom's supply can get scarce. Vitamin A is found in rich red, orange, and yellow fruits and veggies. "In fact, one of the most important things you can do for yourself and your baby is to double your daily intake of colorful foods; have two servings at every meal and one at every snack," says Elizabeth Somer, R.D., author of Nutrition for a Healthy Pregnancy. If you choose to skip the organics, look for produce that says "vine-ripened" or "tree-ripened." They have more nutrients, Somer notes.