While an acorn is not an oak tree, it is still a member of the oak family. There are many phases of development for members of the oak family: acorn, sapling, full grown tree. Similarly, there are many stages of development for members of the human family: zygote, embryo, fetus, newborn, toddler, adolescent, teenager, adult. Humans and members of the oak family look and act differently as they pass through these respective stages, but what they are—their human or oak nature—remains consistent throughout their lives.
An acorn is to a tree as a human female fetus is to an adult woman. It is unfair to ask a fetus to exercise capacities fulfilled by more mature members of her species (e.g., self-awareness). Her developmental maturity is irrelevant to the kind of entity she is. Who we are does not depend upon how developed we are.