By Stephanie Stahl

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PHILADELPHIA (CBS) — It’s being called a fertility first after two women were pregnant with the same baby.

It’s not unusual for both members of a same-sex female couple to participate in a pregnancy. Fertility clinics have long offered what’s known as “reciprocal in vitro fertilization,” where one woman is the egg donor and the other woman carries the embryo. This new path to motherhood takes that a step farther.

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Stetson Lane Coulter is the 5-month-old miracle baby of couple Ashleigh and Bliss Coulter.

“The way that Mr. Stetson came into this world was pretty special,” said Ashleigh Coulter.

When the couple married, they knew they wanted kids and through what’s called “effortless in vitro fertilization,” they were both able to carry their son.

“We gave it a try and it was very, very successful,” said Bliss Coulter.

“This represents the first time that two women have both physically carried their child together,” explains Dr. Kathy Doody of the CARE Fertility institution.

Fertility specialists Dr. Kathy Doody and her husband, Dr. Kevin Doody, made it happen using Bliss’ eggs and sperm from a donor.

“She was so confident when she was saying that they can do it. I think that was surprising to us but also exciting,” recalls Ashleigh Coulter.

Through effortless IVF, instead of placing the sperm and eggs into incubators, they go into an INVOcell, a medical device that was placed into Bliss Coulter for five days. This is when the egg fertilizes and early embryo development begins.

The embryos were then removed from Bliss Coulter and eventually transferred into Ashleigh Coulter, who carried their baby to term.

“This is a revolutionary type of IVF. It’s more accessible, it’s more affordable and it’s truly more natural,” says Dr. Kevin Doody.

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The Coulters say they feel blessed to be able to share this experience together.

“You know your whole life changes obviously with anybody when they have a baby, so leaning on your partner, I think, is really, really important and I definitely think it brought us closer together,” Ashleigh Coulter says.

The INVOcell, which bypasses growing the embryos in a lab, has been used for heterosexual couples. It tends to be less expensive but not as effective.

In this case, one mom carried the baby while the embryo was fertilized and started to grow. That cell is removed, and the embryo implanted into the mom who delivered the baby.