CALIFORNIA (REUTERS) - Little Samantha Lynne will have a story to tell when she can talk.

Her mother, Ms Sarah Mariuz, gave birth on June 30 at 1.18am Pacific Time (4.18pm Singapore time) in California. Her twin sister gave birth at the exact same time, but in Denver's time zone.

"What we joke around and say was a 'twincidence'," said Ms Mariuz.

Sarah says the twincidence started while visiting her sister in Denver for Thanksgiving. That's when her twin Leah shared the news of her pregnancy.

"So instead of saying 'me too' or 'you're going to be an aunt as well' I just jumped up and down and squealed with excitement and was really happy for both Leah and Kyle," she added.

Shortly after, Sarah too spilled the beans.

She said: "No, there was no plan, no collaboration to be pregnant at the same time. It was all a complete shock."

And a happy shock to learn their babies will always share the same birthday and time stamp.