HOUSTON (NBC) -- Valentine's day brought a very special delivery to Tressa and Manuel Montalvo of Houston: two sets of identical twins.
The quadruplets were conceived spontaneously, without the help of any fertility treatments or drugs – something that has a one in 70 million chance of happening, the hospital says. They were born at 31 weeks by Cesarean section to Tressa, who is 36, The Woman's Hospital of Texas in Houston says.
The couple had been trying for one brother or sister to keep their little boy Memphis, now 2 years old, company. At 10 weeks, they learned she was having twins. But when the couple went in for Tressa's 12 week check-up, they learned she was carrying not two, but four babies.
"If I wasn't already on the table lying down, I'm pretty sure I would have hit the floor," Tressa told TODAY.
Manuel's immediate reaction was jubilation.
"The first thing I said was ‘Home run!' and then I started jumping up and down," he said.
The Montalvo's doctor says this delivery is a very rare event.
"The incidence of spontaneous quadruplets is somewhere of the order of 1 in 500,000," said Dr. Brian Kirshon, a specialist in maternal and fetal medicine at Houston Perinatal Associates. "And then if you take two sets of identical twins in the quadruplet set, the incidence must be one in many, many millions. It's an extremely rare occurance."
The day of the delivery, Tressa was both nervous and excited.
"There were all these thoughts coming into my head," she said. "There's four human beings that are about to come into this world that are my responsibility and they are going to be home with me one day. And we are going to be a family of seven. This is amazing."
The Montalvos have always wanted to have a baby girl. And Manuel has told reporters that he'd like to keep trying even with the five boys the family has now.
Tressa isn't ready to commit to anything. "My husband was quick to answer for us in interviews," she said. "For myself, I thought, ‘OK, can we get through this first before I answer that?'"
Ace and Blaine were born at 8:51 a.m. on Feb. 14 and weighed 3 pounds, 10 ounces, and 3 pounds, 15 ounces, respectively. Cash and Dylan followed a minute later, weighing 2 pounds, 15 ounces, and 3 pounds, 6 ounces, respectively.