It has happened many times before. It also feels like a ritual. Mother-to-be would have an ultrasound done. She would ask if the baby was okay. Once she knows everything is fine, she will pop up the next question. Is it a boy or a girl? Talk about all the milestones that science has surpassed or the world has changed with social transformation and women's empowerment; it is pretty comical to see how the response usually is. It is by no means mutually exclusive, but it is seen in the majority. If male genitalia is observed, the mother, the husband or the rest of the spectators, who would sometimes be her sister, mother or mother-in-law, would burst into laughter, which in my mind sounded like joy, not comedic. I even had a mother-in-law who went on to give a loud cheering clap. She must have been a cheerleader in her previous life. Conversely, a similar atmosphere would not be observed if a girl is suspected. As if hoping for the opposite, one of the 'spectators' would blurt...
It is all Mimesis