Final answer:
By the end of the first trimester, the fetus's fingers are well-formed with nails, and the kidneys begin to function. During this critical period of development, other organ systems like the brain and skeletal system continue to mature, and exposure to toxins should be strictly avoided.
Step-by-step explanation:
After completing the first trimester, a woman can be informed that certain fetal structures are well-formed. Among these structures, by the end of the first trimester, the fingers have already developed with the emergence of nails, showcasing significant progress in limb formation. Additionally, the kidneys begin functioning within this period, starting to produce urine. These developments indicate that the fetus's major organs and structures are in place, even though they may not be fully operational, with various organs like the lungs and liver not yet entirely functioning. It's crucial to note that during this critical developmental phase, exposure to toxins can severely impact the fetus's growth and survival, making it essential for expectant mothers to avoid harmful substances.
The first trimester is a critical period for fetal development where the blueprint for the body's organs and structures is laid out. By the eighth week, the term 'fetus' is applicable, with the body essentially formed. From week 9 to 12, further development includes brain expansion, bodily elongation, and the onset of ossification. It's a time of intense growth, setting the stage for everything that follows.