Final answer:
Alpha-fetoprotein (AFP) is the protein that inhibits estradiol from crossing into the female fetal brain, thus preventing its masculinization and allowing for typical female brain development.
Step-by-step explanation:
In a female fetus, alpha-fetoprotein (AFP) is the protein that inhibits estradiol from crossing into the brain, thereby preventing masculinization of the female fetal brain. AFP binds to estrogen, such as estradiol, allowing typical female brain development by preventing these hormones from exerting their masculinizing effects.
During pregnancy, the role of hormones such as progesterone, estrogens, and human chorionic gonadotropin (hCG) is significant. Progesterone inhibits uterine contractions, helping in maintaining the pregnancy, whereas estrogens promote tissue growth. Additionally, hCG ensures the survival of the corpus luteum and stimulates testosterone secretion in male fetuses.
While the provided reference materials focus on a variety of pregnancy-related hormones and their functions, AFP is specifically the protein that protects the female fetal brain from estradiol. This is not explicitly mentioned in the references but is a well-known fact in developmental biology.