Mum-to-be's Fitbit knew she was pregnant before she did.

A New York couple have discovered they are expecting a child – all thanks to the wife’s Fitbit.

The pair had noticed unusual data on the woman's device, and so the husband turned to Reddit to ask for advice or any explanation, assuming it was simply a technical glitch.

He wrote:

My wife's Fitbit is showing her heartbeat being consistently high over the last few days. Two days ago, a somewhat normal day, she logged 10 hours in the fat burning zone, which I would think to be impossible based on her activity level. Also her calories burned do seem accurate. I would imagine if she was in the the fat burning zone she would burn a ton of calories, so it's not lining up.

I'm not sure if something is wrong with the sensor. Is there a way to reset or recalibrate the device? I'd like to try that before I contact customer service about a possible replacement.

Reddit user Thatwasunpleasant offered some advice, posting: "Has she experienced anything really stressful in the last few days or is it a possibility she is pregnant?"

Within a few days, the husband responded, confirming that yes, his wife was expecting.

Reddit users were quick to congratulate the parents-to-be, with Thatwasunpleasant posting "I was right! Holy crap, a Reddit first for me! Congratulations!"

And what about after birth, the reactions to mums and non-mums seeing placenta is hilarious...

The elated dad-to-be also told Buzzfeed he was excited by the news.

“It’s definitely a great story to tell the baby one day about how it happened," he said.

So there you go, ladies - your Fitbit might just replace the good old wee on a stick pregnancy tests...

How did you find out you were pregnant?