01/03/2018 10:40 EST | Updated 01/03/2018 10:40 EST

U.S. Mom Welcomes Twins Born In Different Years

"Big brother was born in 2017. Little sister was born in 2018!"

California mom Maria Esperanza Flores Rios may have welcomed her twins mere minutes apart, but after going into labour on New Year's Eve, the time difference meant her babies were born in two different years.

Rios welcomed her son, Joaquin Jr. Ontiveros, at 11:58 p.m. on Dec. 31, 2017. Her baby girl, Aitana de Jesus Ontiveros, was born 18 minutes later at 12:16 a.m. on Jan. 1, 2018.

The twins were delivered via C-section at Delano Regional Medical Center in Delano, California. Although they were born four weeks premature, reports that the infants are both healthy.

Joaquin Jr., who weighed five pounds, nine ounces at birth, was the last baby that was born in Kern County in 2017, and his twin sister Aitana, who weighed four pounds, 10 ounces, was the first to be born in the county in 2018.

"I've been in the practice for almost 30-plus years. I've never had the opportunity to do anything like that before," said Seyed Tamjidi, who delivered the babies.

While this may be the first time Tamjidi has witnessed twins being born in different years, it's not entirely unheard of. Last New Year's, three U.S. couples welcomed twins, with one who was born in 2016 and the other born in 2017. For one set, the time difference was so close that they were born only four minutes apart!

A Mississauga, Ont. mother also previously welcomed twins with different birthdays, with one born in 2013 and one in 2014. And prior to that, another three sets of U.S. twins were born in different years in 2011 and 2012.

Since Rios gave birth to the first baby of 2018 at Delano Regional Medical Center, she received $3,000US in baby gear, which is an annual gifting tradition at the hospital.

On Facebook on Monday, the hospital wrote that they were "honoured to play a significant role in this 2018 New Year delivery of baby twins."