At 20 weeks babies genitals are usually fully developed so at that stage it's unlikely, I politely asked the sonographer to show me so I could compare between when they showed me my daughters (a white lie 🙈) and she did and explained what bits were what 😋
If babe is in the right position there is no denying it is a boy. It's hard to explain but on the scan they're little willies look like a perfectly draw one like the boys used to draw in school haha
as @ssumner says, it's not uncommon which is why we had a private gender scan and then asked the consultant to double check it was right. With two different confirmations that we are having a boy I am pretty confident that it's right x