Pregnancy sickness, Profet suggested, may have evolved to reduce an embryo’s exposure to natural toxins. She pointed out that women with pregnancy sickness strongly prefer bland foods that do not spoil easily (like breads and cereals) and are particularly averse to foods associated with high levels of natural toxins, such as bitter or pungent foods and animal products that are not extremely fresh. The theory also explains why sickness occurs mainly during the first trimester. That is when the embryo develops organs and is most sensitive to toxins; at the same time, it is small and its calorie
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