Ying Ying becomes oldest first-time giant panda mom at 19. And it's twins.

A giant panda at a Hong Kong animal theme park has given birth, becoming the oldest first-time panda mother on record.

After more than five hours of labor, Ying Ying delivered tiny pink twins at Ocean Park on Thursday, the day before her 19 ^th birthday. Her new family is a 4.3-ounce female cub born at 2:05 a.m. and a 4-ounce male cub born at 3:27 a.m.

“This birth is a true rarity," Paulo Pong, chairman of the Ocean Park Corporation, said in a news release, calling the births of the giant pandas "thrilling news."

He also thanked the park’s animal care and veterinary staff for their work during the years-long process of attempting to have Ying Ying mate with her male companion at the park, Le Le.

“As a first-time mother, Ying Ying was understandably nervous throughout the process. She spent much of her time lying on the ground and twisting,” Ocean Park said in a statement.

“Both cubs are currently very fragile and need time to stabilize, especially the female cub who has a lower body temperature, weaker cries, and lower food intake after birth,” the park said, adding that it will be several months before the public can see the babies.

A birth 17 years in the making

The mating process of the iconic black and white bears is a fraught process, especially in captivity. Determining when a panda is actually pregnant is also notoriously difficult.

While the World Wildlife Fund says that the gestation period for giant pandas ranges between 95 to 160 days, an actual pregnancy can’t be confirmed until 14 to 17 days before birth. Ocean Park only determined that Ying Ying was pregnant via an ultrasound scan on Aug. 11, just four days before the birth.

Ying Ying and her mate, Le Le, arrived in Hong Kong in 2007.

More: Two pandas tried to mate for a decade. With the zoo closed due to coronavirus, they finally did it

Mating happened naturally

In 2020, with Ocean Park closed due to the coronavirus pandemic, the two bears mated naturally for the first time, after a decade of failed attempts.

The park had hoped that this would result in a pregnancy for Ying Ying, but ultimately conception remained out of reach until recently.

The twin cubs, who have not been named, will remain under 24-hour intensive care.

Giant pandas have a lifespan of 18-20 years in the wild and up to 30 in captivity, according to Guinness World Records .

Max Hauptman is a Trending Reporter for USA TODAY. He can be reached at MHauptman@gannett.com

This article originally appeared on USA TODAY: Ying Ying becomes oldest first-time giant panda mom at 19. And it's twins.