Conjoined twin girls separated after nearly two years sharing heart tissue, a liver and a diaphragm

A set of conjoined twin girls have been successfully separated after sharing parts of their hearts for almost two years.

As The Daily Mail reports, Anna Grace and Hope Elizabeth Richards were born attached at the chest and abdomen when they were born on December 29, 2016.

After a year of life in a neonatal intensive care unit, sharing a liver, diaphragm and part of a heart, they were carefully split during a seven-hour surgery on January 13, officials from the Texas Children's Hospital in Houston announced Monday.

The twins are recovering in the hospital, finally in their own beds and are expected to be strong enough to go home in about a month.

'We've thought about and prayed for this day for almost two years,' their mother, Jill Richards said, 'it's an indescribable feeling to look at our girls in two separate beds.'

The twins' parents, Jill and Michael, of North Texas, knew long before their daughters were born that they would be conjoined.

An ultrasound revealed that their daughters were thoraco-omphalopagus twins, meaning they shared large portions of their torsos.

The family could not be certain until after their birth that their daughters could ever live life apart.

After Anna and Hope were delivered by cesarean-section at over 35 weeks, weighing a combined nine lbs 12 oz, they were kept at the hospital to assess their strengths and what vital organs they shared.

About one in every 200,000 live births in the world are conjoined twins. Though there are far more hospitals and surgeons equipped to separate them now than in decades past, about 35 percent of these babies only live a day after their birth. 

Conjoined twins are very rare, making the causes behind the condition difficult to study and as-of-yet unclear.  

Twins form when a single fertilized egg splits early in embryonic development. 

But this process is not instantaneous, and on the rare occasions when the egg does not fully split, the two fetuses become conjoined, growing shared organs and body structures. 

Their bodies may be linked at nearly any point, though thoraco-omphalopagus twins, like Anna and Hope, are the most most common form, making up about 28 percent of all conjoined twins.  

Doctors are unsure why, but conjoined twins are usually girls - about 70 percent of the time - and tend to have better survival rates than boys do after birth.

Twin girls also tend to be more resilient to the stresses of separation surgeries, and now, at least one twin survives separation about 75 percent of the time, though rates vary depending on what organs and structures the babies' share. 

Success rates for separating twins joined at the spine, for example, are estimated to be as high as 68 percent. 

The first separation surgeries were performed in the 1950s, but the operation remains a steep challenge to even the most experienced surgeons. 

For many sets of conjoined twins, separation is simply not an option because they share too many essential organs and blood vessel connections. 

For still other families, separation may cost one twin their life, but give the other a better chance at survival and a more viable future. 

Fortunately for the Richards family, both Anna and Hope had good chances of surviving the surgery, so doctors went to work preparing the pair of babies from the first days of their lives.

The process of separating Anna and Hope would take nearly another two agonizing years after their birth. 

In November, surgeons operated on the baby girls to place tissue expanders in preparation for their separation.

Finally, after a year of round the clock care from three teams of nurses and neonatal specialists, the girls' tiny bodies were ready.

A team of 75 surgeons, specialists and nurses that had been practicing the delicately coordinated operation for months performed a surgery to separate their heart, diaphragm and liver, and to give separate blood sources to the newly-formed two hearts. 

Anna and Hope's surgery required cardiologists to split the parts of their hearts they shared, plastic surgeons to carefully place the once shared tissue over the newly-individual bodies. 

Among the steepest challenges of a separation surgery is the rerouting of blood vessels to make sure that neither twin loses too much blood in surgery, and that all of their organs have consistent supply throughout their new lives apart.

This was particularly true for Anna and Hope, who shared a large blood vessel connecting their partially-conjoined heart. 

'Through simulations and countless planning meetings, we were able to prepare for situations that could arise during the separation,' said Dr Larry Hollier, the surgeon-in-chief and chief of plastic surgery at Texas Children's Hospital.

'We are thrilled with the outcome and look forward to continuing to care for Anna and Hope as they recover,' he added.

The girls will stay in the neonatal intensive care unit until they are strong enough to go home with their parents and older brothers, Seth and Collin.  

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