This is the heartwarming moment a librarian learns she will become a grandmother on her birthday with a series of Dr Seuss-themed clues.

The woman, Colleen, is seen opening gifts on her birthday in a recorded Skype conversation with her daughter, Leah, and son-in-law, David.

While the first gift is fairly innocuous, the second gift - The Cat in the Hat by Dr Seuss - raises some eyebrows.

Colleen rejoices as she learns she'll become a grandmother.

But then she opens her last gift - matching babygrows emblazoned with "Thing 1" and "Thing 2".

David, who uploaded the clip, wrote: "Leah never told her parents we were trying.

"She had always said, 'I'm not having kids' even repeating this about two weeks prior. It was a total shock and surprise to have one baby let alone two."

The couple live in San Fransisco while Colleen and her husband live in South Carolina.

The clip was filmed in May 2013.