(ABC News) -- Talk about a labor of love. Susie Kozisek, a Delaware mother of four, ages 20 to 30, gave birth to her own twin granddaughters, Hallee and Hadlee.
Kozisek, 53, acted as a gestational carrier for her daughter, Ashley Larkin, because Larkin has pulmonary hypertension and cannot get pregnant. Before giving birth to the twins in July, she was also the gestational carrier for Larkin's older daughter, Harper, born in June 2011.
A gestational carrier volunteers to carry a pregnancy for another woman who cannot carry a pregnancy for herself. The eggs and sperm are harvested from the biological parents and united through in vitro fertilization. The resulting embryo is then implanted in the carrier's uterus.
"I heard about the procedure on a talk show and decided to check out the possibility of me doing this for them so they could have kids of their own if they wanted," Kozisek said.
Larkin said she considers her children a blessing and a miracle.
"I've always been close with my mom even before this so that hasn't changed and I'm grateful she will have such a special bond with her grandkids," Larkin said.
The embryos for the Larkin twins were kept in storage since an in vitro fertilization took place in October 2010 at the Mayo Clinic. They were implanted in Kozisek's uterus in November 2012.
Both pregnancies were uneventful, Kozisek said, similar to the pregnancies with her own children. She stayed healthy throughout and was able to continue her job as a legal secretary for the duration. Larkin was in the delivery room when her daughters were born.
Dr. Janie Jensen, the Mayo Clinic fertility doctor who performed the in vitro fertilizations for the family, said the circumstances surrounding the twins' birth were extremely uncommon.
"It's usual for a mother to act as a gestational carrier for her own child and she was at the older end of the spectrum for pregnancy," Jensen said. "But she was a good candidate because she'd carried previous pregnancies successfully and was in excellent health."
After discussing it within the Mayo Clinic fertility group and consulting with high-risk pregnancy experts, Jensen gave Kozisek the green light. As a doctor, she was delighted with the results.
"They are a testament to the profound love a mother can have for her child," Jensen said. "It is an incredible thing this mother did so her daughter could have children."