Jess Johnson, of Cheshire, paid for a private scan so fiance could see their baby.
David hadn't been allowed into hospital appointments due to Covid restrictions.
But parents were gobsmacked when cheeky son flashed them the middle finger.
A couple were left shocked after their unborn baby boy flipped them the middle finger during a 4D scan - with the first-time mother now convinced her son will be a 'handful'.
Jess Johnson, 24, from Nantwich in Cheshire, paid for a private scan so her fiance David Lewis, 23, could see their baby after not being allowed into hospital appointments with her due to coronavirus restrictions.
But the parents were gobsmacked when their cheeky son flashed them the middle finger at the end of his 30-week scan.
Hilarious 4D scan photos show the little boy covering up his face, yawning - and then appearing to flip the bird directly at his watching parents.
Jess joked that the baby seemed to be telling his parents that he'd had enough pictures taken as he made the rude gesture.
The couple also claimed their unborn son must take after his dad, with HGV mechanic David warning that their son may be a 'little terror' if he follows in his footsteps.
Jess said: 'It was nice for my partner to see him as well, as I don't think he would have believed me if I told him what he did.
'We went in and they started scanning me. He was a bit shy. He'd been shy in previous scans but he was covering his face up and giving a few yawns as if to say he was getting tired now.
'Towards the end of the scan he started to cover up again as if to say, "you've had enough photos, now leave me alone". We were trying to get a couple more as we didn't have that many.
'Five minutes before the end he decided to give us the middle finger instead as if to say "that's enough mum and dad, leave me alone now".'
She added: 'My other half saw it but didn't immediately clock on to what happened. Me and the sonographer both looked at each other and said, "did he just stick the finger up?".
'She said, "I think so", so we went back on it. She rewound it a little bit.. We were quite shocked and even she was quite shocked to be honest.
'He sort of put it up and then put it back down as if to say, "I didn't mean to do that". As if he knew it was naughty but he still did it anyway, bless him. Once he's born, I will just be laughing at him more than anything, I think.'
Courier Jess, who is now 38 weeks pregnant, says the couple can't wait to meet their son.
She said: 'He will definitely be cheeky. We know he's going to be a handful. I've got two dogs as well so I can imagine it will be a crazy house with all three of them together.
'Dave is definitely cheeky sometimes. I say he takes after his dad in every way so he's probably like his dad. He's definitely stubborn like his father.
'I don't think he's going to come on time because, if he's like his dad, he leaves everything to the last minute. I think he'll be like him. It's in his genes, bless him.'
Her fiancé David, from Liverpool, was thrilled he was able to be in the scan room to see the little boy's finger flash.
David said: 'I'm overwhelmed and excited to be a dad. It's our first baby so we don't really know what to expect. It's going to be a big life change in itself getting everything prepped and ready. We're over the moon.
'I was emotional when I first saw him. When I went into the first scan and there was a fully grown baby with full features, it was crazy. It was really overwhelming.
'I did see the moment where he flashed the middle finger on the scan. I laughed. I was shocked - even the lady doing the scan couldn't believe it. I think she took a picture herself because she couldn't believe what he'd done.
David added: 'He takes after his dad. He's probably going to be a little terror if he takes after me. I've showed [the scan photo] to friends and family, to everyone. A lot of people came up to me and said, "that scan is amazing". It's had a lot of attention.
'Everyone has been shocked in a good way at how he's managed to do this. We can't wait for him to be here. It's life-changing. It's going to be amazing.'