And that is exactly what happened to Kim Guiley and her husband Travis, from California, when they welcomed their second baby back in July.
The parents, who already have a daughter, were so convinced that they were having another little girl so didn’t bother to officially find out at the ultrasound scan.
But a photograph taken straight after the birth shows just how shocked the parents were when they were handed their newborn son, Theo.
Guiley told TODAY: “I opened his legs and was just shocked. I mean, you saw the look on my face, you can’t make up that look. It was very surprising, and I didn’t realise how much I was hoping for a boy until that moment.”
The 28-year-old said that she had persuaded herself with lots of “silly reasons” she wasn’t going to be having a son: “I was really sick with this pregnancy and there’s a correlation between sickness and having girls, so I think that partially contributed, too.
“And my two-year-old daughter thought it was a girl.”
The mother, who had a home birth, believes she also subconsciously chose not to learn the baby’s gender because of a miscarriage she suffered in 2015.
Instead of focusing on the gender, she just wanted a healthy child.