Final answer:
The statement is true; the embryo is highly susceptible to damage from substances consumed by the mother during the first trimester due to the development of major organs and body systems.
Step-by-step explanation:
True, the embryo is most susceptible to damage from substances the mother ingests during the first trimester. During the first eight weeks after fertilization, all the major organs are forming, and this is known as the embryonic stage. It is a period of particularly high vulnerability because the developing body systems are undergoing critical growth processes.
Exposure to harmful substances such as alcohol, illegal drugs, and some medications during this time can result in significant damage to the developing embryo, potentially causing a range of birth defects or developmental issues. This sensitivity to teratogens is due, in part, to the development of the placenta, which allows nearly everything the mother ingests, including toxins, to reach the developing embryo.