Double the joy ... A woman has had two sets of twins at once.

Double the joy ... New sets of twins Ace and Blaine, and Cash and Dylan.

At a 10-week scan, Tressa Montalvo was surprised to learn she was pregnant with twins. At another scan two weeks later, she got the shock of her life when she learnt she was pregnant with not just one set of twins, but two – she was carrying four babies.

In fact, she was having two sets of identical male twins.

“If I wasn’t already on the table lying down, I’m pretty sure I would have hit the floor,” Tressa, already a mum to two-year-old son Memphis, told TODAY.com.

New parents times four ... Tressa and Manuel Montalvo with their doctor.

New parents times four ... Tressa and Manuel Montalvo with their doctor.

Her husband Manuel, however, was thrilled. “The first thing I said was ‘home run!’ and then I started jumping up and down,” he said.

Tressa, 36, from Houston, USA, says that before the babies were born she was understandably nervous – but excited, too.

“There were all these thoughts coming into my head. 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.

“We are going to be a family of seven. This is amazing.”  

The babies were born via caesarean at 31 weeks on Valentine’s Day – first came Ace and Blaine (1.64kg and 1.78kg respectively), then Cash and Dylan (1.33kg and 1.53kg). And yes, Tressa says the A-B-C-D pattern of their names was intentional. 

The chance of having two sets of identical twins – who were conceived spontaneously, without any fertility treatment or drugs – is as low as one in 70 million, according to The Woman’s Hospital of Texas, Houston, where the babies were born.

“The incidence of spontaneous quadruplets is somewhere in the order of one in 500,000,” said a local specialist, Dr Brian Kirshon. “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 occurrence.”

When reporters asked if they would have any more children, Manuel said that the couple had always wanted a girl, and that he’d like to keep trying for one.

Tressa, however, isn’t so sure. “My husband was quick to answer for us," she said. "For myself, though, I thought, ‘OK, can we get through this first, before I answer that?’” 

See what Essential Baby members have to say about this story in our forum. You might also like to read our parents of multiples forum