Although getting serious statistics on the matter is not easy, the estimated numbers can be surprisingly high (e.g: "One in 25 fathers is not biological parent": https://www.theguardian.com/society/2005/aug/11/childrensser...)
If suddenly we discovered an easy way to give a hint you should do a DNA test, it could do some serious noise.
Many years ago my father was once given hospital test results stating he was terminally ill with a heart condition. He knew he was somehow given a different patient's test result under his name when when his family doctor asked him if he exercises (he does) and the doctor said "That can't be your patient record. You wouldn't be able to exercise if your heart was as sick as the test result states." My father is still alive and exercising regularly today.
I wonder if its brains you smell, and a fully fused skull prevents the smell from escaping.
As a teen, I once got heckled by some coworkers. "Wow, are you pregnant? Your face is radiating!" I had accidentally put on too much oily sunscreen that day. I'm a cis male with a beard.
It's not so much an obvious smell as a perceived "sharpness" that feels related to the sense-modality of smell, but is not exactly equivalent to it. I wonder sometimes if it's a pheromone-based phenomenon.
I can often smell when my wife is in a bad mood (her breath literally smells sour). However, it isn’t a reliable indicator (many false negatives).
The thing here is that babies have this ethereal and indescribable effect on the people around them which postmodernist science is now trying understand.
(Damn, now I want to have more babies, but we're almost 10 years past that possibility. And still nowhere close to grandkid babies.)
Similar effect in how they look for different people.
One thing I have noticed is they smell worse as they get older :)
Studying human behavior is difficult. It is possible that only women can smell the pheromone, or it can be culture. Its hard to untangle unless one do blind studies.
Did you get these remarks from women, and were they aggressive (as the study says)?
As an uncle I remember smelling top of baby's soft spot and thinking it was pleasant. Maybe it was the Johnson's product or talcum or some other baby product.
Of course, they can also smell like mother's milk if they puke it up and that shit smells sour.
I've also noticed puppies have a pleasant smell to before they get older and their breath stinks cause the owners don't brush their teeth enough.
My first kid stopped having the new baby smell before she started smiling, and that period in between was hard. (My second kid started smiling before the smell wore off. She's my favorite.)
As a side note my wife and I are convinced going fruits first was not ideal as our 6 month old now loves her fruits but hates her veggies. We saw this coming but figured it better to listen to our pediatrician.