Ever since they were little, sisters Joy Lagos and Maeapple Chaney have been close.
"She was always standing up for me," Lagos said of her sister. "She was always making sure that I was taken care of."
While they have shared much over their lives, a recent pair of operations has brought them even closer.
When Lagos suffered from cancer, Chaney donated the bone marrow needed to save her life.
And when the cancer treatment rendered her sister sterile, Chaney donated an ovary to give Lagos a chance at conceiving.
The procedure was performed by Dr. Sherman Silber, director of the Infertility Center of St. Louis at St. Luke's Hospital in Chesterfield, Mo., and author of the book "How to Get Pregnant."
This operation, performed on Feb. 5, is believed to the first whole-ovary transplant ever done in the United States. And the fact that Lagos and Chaney are not identical twins makes the surgery even more remarkable.
While Lagos will have to wait three months to see whether the transplanted ovary allows her to ovulate and conceive normally, Silber and other fertility experts are already looking at the advancement as a possible therapy for more women in years to come.
The advanced microsurgery required to transfer one of Chaney's ovaries into Lagos' body was a feat of medicine that would not have been possible years ago.
"Technically it is very difficult, because the artery that supplies the ovary is tiny," Silber said. "It's about a third of a millimeter in diameter. This is about a smaller blood vessel you could ever imagine."
Because of this, much of the work had to be done under a microscope, and the stitches were made using a thread and needle invisible to the naked eye.
Another issue that would normally have made the transfer difficult -- or even impossible -- was that of compatibility.
Normally, a recipient's immune system will reject tissue from a donor, even if that donor is a sister or other close relation. Only identical twins would normally have immune systems so similar that sustained doses of immunosuppressive drugs would not be necessary.
In an odd twist of fate, though, the same bone marrow transplant that saved Lagos' life from cancer had the side effect of making her immune system compatible enough with that of her sister's for her to accept the ovary.
"The reason they were perfect, is because Joy had already gone through the immune suppression that would be necessary for a nonidentical transplant," Silber said.
"There was no question mark about it. We knew there would be no fear of rejection."
Silber has also carried out such procedures on twins. In 2004, he transplanted strips of ovarian tissue from a fertile twin into her prematurely menopausal sister. That woman, Stephanie Yarber, has since given birth to two children.
Since then, Silber has performed similar surgeries on six other sets of twins, but the case involving Lagos and Chaney marks the first time he has transplanted an entire ovary.
If the surgery is a success, the transplanted ovary could function normally for decades -- far longer than the one year to two years offered by strips of ovarian tissue.
"I think the ovary is going to last a lifetime," Silber said. "That's the advantage of doing it this way."
Silber said the procedure was a fairly simple one for Chaney; her ovary was removed through her belly button in a relatively quick procedure.