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If you're pregnant, you're understandably cautious about the health risks your beauty regimen might pose to your unborn child -- right down to your shampoo. Your best bet is a shampoo with all-natural ingredients, but read your labels carefully. Some brands tout their herbal earth magic, but still sneak in some questionable ingredients.
Phthalates make up a class of chemicals primarily used to makes plastic soft and pliable, but are also sometimes found as components in certain artificial fragrances. Phthalates are known to cause hormonal disruption in utero and cause birth defects. Therefore, it's best to avoid any shampoo with unspecified "fragrance" in the ingredients list while you're pregnant.
Two preservatives in particular that aren't uncommonly found in shampoos may be no-nos for pregnant women. The first are parabens. The FDA considers parabens safe, but there's some evidence that these compounds can mimic estrogen in the body -- and thus disrupt developmental hormonal activity. This is of greatest concern as a possible factor in breast cancers, but might also pose risks to a developing fetus. Parabens are easily absorbed through the skin, which is why you should avoid them in your shampoo if you're pregnant. Formaldehyde is also used in small amounts as a preservative in cosmetics and shampoo. It's a known carcinogen and may cause birth defects too, although evidence is mixed. Industrial workers, medical staff and other professionals who work with large concentrations of this chemical are probably more at risk than shampoo users, but you might want to be on the safe side nevertheless.
P-phenylenediamine, also known as PPD or PPDA, is a coloring agent found in some shampoos. It's a suspected neurotoxin and teratogen -- that is, it might cause birth defects. It's also a major skin irritant and allergen. Don't panic yet, however -- it's probably not absorbed in any significant amount through your skin, so actual danger may be low. Again, this is a case of better safe than sorry.
Anti-dandruff shampoos and anti-lice shampoos can contain strong chemical compounds that may pose a risk to your developing baby. For dandruff, avoid shampoos that contain salicylic acid, coal tar or the antifungal ingredient ketoconazole. For head lice, manual removal may be preferable to a medicated shampoo -- but consult with your doctor first.