A pregnant woman's late-night walk in a Vancouver park turned dramatic when she delivered twins, apparently long before her due date.

Constable Randy Fincham of the Vancouver Police Department said a man summoned officers who were directing traffic across the street at 11 p.m. Wednesday, saying a woman had just had a baby.

"It appears this woman was caught off guard, went into labour early and it was fortunate that there were other people there at the time," Fincham said.

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He said the 33-year-old woman who lives in the area delivered one tiny infant in Oppenheimer Park, and seemed to be surprised to still be in labour.

"These babies were delivered a lot sooner than was expected by the mother and definitely a lot sooner than was expected by the medical professionals that were looking after the woman at the time."

The boy and girl weighing less than two kilograms each are apparently doing well, and their mom is resting after what would have been a traumatic event, Fincham said.

Delivering babies isn't part of basic training for police, but the two female officers were glad to be there to help before paramedics arrived.

"It's not something where any of our officers start their shift, thinking that they will be out there tonight to welcome a newborn baby in the world," Fincham said. "But it was one of those unique set of circumstances that ended well for everybody."

The officers and the paramedics are also resting after an eventful night.