A Texas woman bagged a one-in-70-million-opportunity when she delivered two sets of identical twins in a Houston hospital on the Valentine’s Day.

Thirty-six-year-old Tressa Montalvo gave birth to four babies - two sets of identical twins at the Woman's Hospital of Texas in Houston. Yet the babies are not quadruplets, as they are share two different placentas, which make them two sets of identical twins, a news release from the hospital said.

The babies were born after 31 weeks of pregnancy through Caesarean section.

Tressa Montalvo and her 43-year-old husband Manuel Montalvo, Jr. had planned the pregnancy and did not use any fertility drug. They had hoped for a little brother or sister for their two-and-half-year-old son, Memphis, the release said.

“We were trying for one little brother or sister for our two-and-a-half year old son, Memphis.” Tressa said, adding, “No fertility drugs were used. We planned the pregnancy―I guess we just succeeded a little too much!”

Montalvo’s physician had told them to expect a set of twins when she was 10-weeks pregnant. Later, on a subsequent visit, the doctor detected a third heart beat after which they were referred to a maternal fetal medicine specialist, Dr Brian Kirshon, who informed them they were going to have two sets of twins.

“We couldn’t have been more surprised when Dr. Kirshon told us we were having four babies and that they were two sets of twins,” Manuel Montalvo said according to the release.

The chance of delivering two sets of naturally occurring identical twins from different placentas is rare - somewhere in the range of 1-in-70 million - according to the hospital. In this case, two boys shared one placenta and other two shared another placenta. In the case of quadruplets, all the four babies will normally share same placenta.

Montalvos named the babies following the A-B-C-D theme. Ace and Blaine, were born at 8:51 a.m. weighing 1.64 kg and 1.79 kg respectively, and Cash and Dylan were born a minute behind, at 8:52 a.m. weighing 1.33 kg and 1.53 kg respectively.

“We tried to stick to the A-B-C-D theme when naming them,” Tressa said. “We didn’t expect it, we were trying for just one and we were blessed with four.”

According to the hospital release, Montalvos are not done yet as they “want a girl."