A woman's body can create a new human with new body parts, but cannot create new body parts for herself as the woman's body needs help from a man to actually create the new human.
Without the sperm from the man, fertilizing the egg in the woman, the woman's body is unable to create the baby or new human.
Also the sperm has to be fertile and not all sperm will be viable to create the baby.
Fertilized eggs divide into cells that grow into an entire baby human, not just one body part.
Most academic philosophers also argue that the fetus should be considered part of the human species, as it shares our genetic code, and, if unimpeded in it's development, will grow and mature into an adult human being.
A human baby forms in the mothers womb through fertilization of an egg by a sperm, creating a single cell that rapidly divides as it travels to the uterus, implants, and develops into an embryo (first 8 weeks) and then a fetus, with major organs and structures forming, nourished via the placenta and umbilical cord, until birth.
The human baby making process and pregnancy involves fertilization or conception, journey to the uterus, implantation, embryonic stage which is weeks 1 to 8 and the fetal stage which is week 9 to birth.
For the fertilization process, a sperm fertilizes an egg in the fallopian tube, which forms a single cell called a zygote.
Then the zygote divides into a ball of cells called a blastocyst as it moves to the uterus, which is a journey that takes around 1 week.
The blastocyst then burrows into the thickened lining of the uterus, and begins pregnancy and triggers hormone production.
During the embryonic stage at weeks 1 to 8, cells differentiate to form major systems like the brain, spinal cord, heart and organs and the placenta and umbilical cord form and provide oxygen and nutrients to the bay.
And by week 8, the embryo has recognizable human features and internal organs.
Then at the fetal stage which is from week 9 to birth, the embryo is now a fetus and growing rapidly, limbs, fingers, toes and facial features also become well defined and organs mature and the baby gains weight and develops reflexes and prepares for life outside of the womb.
The entire process of a baby growing and developing in a mothers womb, is from a single cell to a fully formed baby, is a complex series of cell multiplication, differentiation and structure formation, which is all supported by the mother's body and is an amazing process.