When Mercedes and Jonathan Sandhu found out they were pregnant with quadruplets, joy quickly gave way to anxiety. “We were terrified parents,” Jonathan, who, like his wife, is an engineer, said. “If anyone ever looks up things about higher order multiples, everything is daunting.”The Sandhus had a 1 in 15 million pregnancy. Those are the odds of monochorionic quadruplets, four kids with identical DNA sharing the same placenta. Only about seventy-some-odd cases of monochorionic quads have been recorded in the world. Many quadruplets, sadly, do not survive to birth (one study found a 30 percent neonatal mortality rate). Texas has been home to some of the most recent successful cases —Dallas’s Jenny and Chris Marr welcomed four identical boys on March 15, 2020—but this was…