system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the reason for morning sickness and other"symptoms" in pregnant women? What, if any, are the advantages to us as a species?

They just seem to affect women so much at such a critical stage of human life that I always wondered why it happens.
gpt
(Biologist) Pregnancy sickness prevents the mother ingesting harmful toxins that could damage the embryo. As the embryo is developing (internal organs, limbs etc.) it is incredibly sensitive to toxins that would usually have no effect, e.g. asparagus is fatal to hamster embryos but is a perfectly suitable food for adults. Pregnancy sickness causes retching when these toxins (usually bitter tasting) are detected. It is incredibly useful: women who experience pregnancy sickness (about 75%) are half as likely to have a miscarriage than women who don't.