(CBS NEWS) -- The Larkins of Iowa have two new bundles of joy thanks to a very special woman -- the twins' grandmother.

"Theyare so much Ashley and Jay's. I never considered them to be other thantheir babies," 53-year-old grandmother and gestational carrier SusieKozisek told "We just love to be with them and spoil them."

Thenewborns, named Hadley and Hallie, mark the second and third babiesthat Kozisek has carried for her daughter, Ashley Larkin.

Larkin,28, was told it was too risky to get pregnant because she had pulmonaryhypertension. The condition causes high blood pressure in the arteriesof the lungs, which makes the right side of the heart work harder thannormal.

Larkin and her husband Jay decided that they were going to try to adopt children, until Koziesk made her generous offer.

Kozieskhad been watching a talk show that featured gestational carriers, whoare women who carry and deliver a child for another couple or person.She went to her doctor to see if it was feasible for her, and was toldthat she would be a good candidate because she didn't have pre-existingconditions like high blood pressure or diabetes. Larkin admitted thatthe couple did have some concerns about her mother carrying their firstchild, especially since she was 50 at the time.

"She was more than willing to try so we gave it a shot," Larkin explained to

Inthe Larkins' case, the genetic material from the egg and sperm camefrom the husband and wife, and their fertilized eggs were implanted intoKoziesk. Because Kozeisk has already gone through menopause, she had togo on hormone treatments as well to prepare and keep her uterus in thestate it needed to be to bear children.

The first pregnancy,which resulted in the couple's daughter Harper, went so smoothly thatthey decided to ask Koziesk if she was interested in giving her firstgranddaughter a sibling.

However, this time around there weresome issues. The family's fertility expert Dr. Jani Jensen, an assistantprofessor of obstetrics and gynecology at the Mayo Clinic in Rochester,Minn., told that typically the cutoff age for gestationalcarriers in the U.S. is about 51.4 years old, which coincides with theaverage age of menopause. Koziesk was 52 when she was approached for thelatest plan.

"We took into serious consideration her age from anethical medical standpoint," Jensen said. "But she had done really wellwith the first pregnancy, and this family still had embryos availablein storage. If we didn't use them on Suzie, we would have to get rid ofthem entirely."

Jensen said her team has handled about two dozen gestational carrier cases.

"I'vedefinitely had sisters carry for sisters, cousins carry for cousins,but I've never had a parent carry for a child," she admitted.

Whatno one was counting on was both embryos that were implanted would endup attaching themselves to the uterine wall, resulting in twins.

"(Iwas) shocked, and not quite as confident as I had been when we startedthe process with Harper," Koziesk admitted. "You just wrap your headaround it and just trust the doctors."

Jensen explained that thepregnancy was high-risk, not only because of Koziesk's age, but becauseshe was carrying multiple fetuses. However, outside of a couple extradoctor's visits and ultrasounds, Larkin said there wasn't much extrawork needed to be done for this pregnancy.

"I'm amazed at howwell she did," Jensen said. "I've had patients who are two or threedecades younger who didn't do as well in pregnancy as she did. I thinkshe's a real role model."

Larkin was in the delivery room whenher daughters were born via C-section. They didn't know they wereexpecting girls until they came out, which was a nice surprise for thecouple.

The family has their hands full -- so there's no talk oftrying again or adopting a boy -- but the possibility is always there.For now, they're enjoying their three young girls.

"(The kids) are her world obviously," Larkin gushed. "You can just tell there's a special place in her heart for those kids."

Asfor Koziesk, she only spent three days in the hospital. She saiddoctors told her that these gestational pregnancies would not be as easyas her previous four children, but Koziesk admitted she really didn'tfeel a difference. A month after giving birth to twins, she was back towork at her part-time job.

"I didn't have to get up at night withbabies," Koziesk said about her quick recovery. "I can come and helpher when I want and visit the babies when I want -- and go home."

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