here's an article:
and here's something beautifully written that i think you will like:
"Perhaps the greatest myth surrounds pregnancy. Many believe the uterus is simply an incubator. Nothing could be further from the truth. The most important aspect of all pregnancies- including egg donation pregnancies- is that as the fetus grows, every cell in the developing body is built out of the pregnant mother's body. Tissue from her uterine lining will contribute to the formation of the placenta, which will link her and her child.
The fetus will use her body's protein, then she will replace it. The fetus uses her sugars, calcium, nitrates, and fluids, and she will replace them. So, if you think of your dream child as your dream house, the genes provide merely a basic blueprint, the biological mother takes care of all the materials and construction, from the foundation right on up to the light fixtures. So, although her husband's aunt Sara or the donor's grandfather may have genetically programmed the shape of the new baby's earlobe, the earlobe itself is the pregnant woman's "flesh and blood." That means the earlobe, along with the baby herself, grew from the recipient's body.
That is why she is the child's biological mother. That is why this child is her biological child."