Consider two pregnant individuals. Individual A receives regular medical check-ups, maintains a nutrient-rich diet, and avoids all known harmful substances throughout her pregnancy. Individual B, unaware she is pregnant for the first two months, continues to consume alcohol regularly and is exposed to a significant viral infection during that time. Based on general principles of prenatal development, compare the potential developmental risks for the two fetuses. In your analysis, explain why one fetus faces a greater risk of developing structural abnormalities and justify your reasoning by discussing the relationship between the timing of an exposure and its potential impact.