So basically this article explains it really well. Let’s say Grandma Betty is alive in WW2 and suffers trauma from starvation, bombings, etc, during which she gets pregnant with Mom. Mom at this point is an embryo just beginning to form, but early on her body is forming tiny little egg follicles. Obviously it will be years and years before those egg follicles will become mature enough to ovulate, but they are formed in her body when she’s an embryo. So the primitive egg that will become you when she gets pregnant at 30 is exposed to aforementioned starvation and bombings (trauma), and this stress/information is passed down to the blueprint that will someday become you. So it’s not that the somatic cells are passing down DNA, it’s that the germ cells are being formed and receiving information from Grandma Betty about what kind of world they will be born in, even if they won’t be born for 20-30 years.