The Greater Baltimore Medical Center said the mother, identified only by her first name, Jennifer, 38, had been in labor for 33 hours and the baby's head appeared just as Tuesday afternoon's earthquake began, The Baltimore Sun reported Thursday.
Jennifer's husband, Tom, 39, said he was confident in the building's ability to withstand an earthquake because it had been designed by his firm.
"I was certain the building was sound and everything would be OK," he said.
Hospital spokesman Michael Schwartzberg said baby John was born at 8 pounds, 11 ounces.
"We've had babies in other storms that Mother Nature has brought us," Schwartzberg said. "As far as I know, this is the first baby born in an earthquake."
"On the other hand, it was another normal day for labor and delivery. You never know what will come through those doors," he said.