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Describe the course of Han China's struggle with the Hsiung-nu.
Birth Defects
Conditions that are present at birth affecting the structure or function of the body, ranging from mild to severe.
Teratogens
Agents or factors that cause malformation of an embryo or fetus, including certain drugs, infections, and chemicals.
Embryonic Stage
The period during pregnancy from the second to the eighth week post-conception, when significant growth and development of the embryo occur.
Gestation
The period of time a fetus develops inside the mother's womb or uterus, typically lasting about 40 weeks in humans from the last menstrual period.