‘It's Scott's Baby!'

The‘co-parents’ have been getting busy... and another little one is on the way!

They’ve been joined at the hip of late and now Kourtney Kardashian and Scott Disick’s relationship has taken a stunning new turn... because she’s pregnant with his baby!

Yep! NW can reveal the exes – already parents to adorbs kids Mason, nine, Penelope, six, and Reign, four – have been hooking up for no-strings attached romps for months, despite Scott’s ongoing romance with Sofia Richie.

It’s resulted in a bun in the oven for the sexy mama, 40, and sources say she couldn’t be happier! “She’s been keeping this secret for a while but apparently Kourt’s just past the three-month mark and her due date is around Halloween,” an insider reveals. “She’s overjoyed this has happened, even if they didn’t intend for her to get pregnant. Word is, she conceived when they got together for some naughty fun after a few drinks at her place. One thing led to another, they had an incredibly passionate time between the sheets and before Kourt knew it, she was taking a pregnancy test. She was over the moon when she found out!”

As NW readers know, Kourt and Scott officially parted ways in mid-2015 after she grew sick of his hard partying and hook-ups with other women.