Scientists at the Children's Hospital of Philadelphia have successfully grown lambs inside an artificial womb.

Eight lambs born at equivalent of 23 weeks human gestation were kept alive by placing them inside a "biobag, " which looks like a huge ziplock that is attached with tubes of blood and fluids. Details about the breakthrough experiment have been published in the journal Nature Communications.

According to The Atlantic, the lamb fetuses were able to survive for four weeks and are still surviving at present, which is longer than previous attempts. Their brains and organs developed without complication. They even started to grow wool and began opening their eyes.

The biobag is filled with synthetic amniotic fluid while a tube that provides nutrition and oxygen and removes carbon dioxide is attached on the umbilical cord of the fetus.

As clarified by the researchers, their primary goal is not to eliminate the vital role of mothers in pregnancy but to give premature babies a chance to survive by placing them inside a uterus-like environment that will nurture and protect them until they are fully developed.

As per Science Alert, the leading cause of infant mortality and morbidity in the U.S. is premature birth. Those babies born before 25 weeks have low chances of survival.

In a video titled "Recreating the Womb: New Hope for Premature Babies," Kevin Dysart, a neonatologist at the Children's Hospital of Philadelphia, says only about half of the 30,000 American babies who were born prematurely survive. And those that survive usually have to deal with disabilities.

The researchers are hoping to accomplish the whole course of the study in two years. If approved, they will begin to test the sac on premature human fetuses.

Meanwhile, Dena Davis, a bioethicist at Lehigh University, who is not involved in the study raised some potential ethical concerns if the technology is tested on human fetuses.

"If it's a difference between a baby dying rather peacefully and a baby dying under conditions of great stress and discomfort then, no, I don't think it's better," Davis told National Public Radio.

"If it's a question of a baby dying versus a baby being born who then needs to live its entire life in an institution, then I don't think that's better. Some parents might think that's better, but many would not," she says.