Genetically, a boy has XY chromosomes and a girl has XX chromosomes (apart from some genetic disorders that you would probably already know about if you had them), so you can run a DNA test if that level of certainty is needed. Otherwise, a boy will have a penis and testicles and a girl will have a vagina (and ovaries inside).
Now, sometimes people are born with something called "ambiguous genitalia," and this means that they were born with genitals that didn't end up developing in the same way as most people's genitals do. In these cases, a DNA test should be done to make sure that you don't socialize someone to the correct sex. Some people are born with genetic conditions such as intersex (which used to be called hermaphroditism) or "disorders of sex development" (DSD). A doctor can go through the varies forms of DSD and help a person with a DSD to determine if they are a boy, a girl, or something in between or combined--and if so how to deal with that in a way that has a good outcome for that person.
you dont unless you have ultrasound.
There are different ways to tell, but all of them have to be performed by a doctor. As there are no means in an everyday household to predict the sex of a baby, your way of knowing whether you are going to have a boy or a girl is going to the doctor and having him check.
Look down below well....... if your a boy your annoying ! :)
if your a girl your big headded :) look between your legs you will then no
how do i tell if my my turtle is a girl or a boy?...
you cannot tell if the caterpillar is boy or girl
can you tell if a fish is a boy or girl by the tail
its harder for a boy to tell if a girl likes him
YOu can not tell the difference between a girl or boy starfish.
by asking its mother if it is a girl or a boy and plus you can tell by the face
you can tell if its a girl or a boy byits butt or eyes. if its a girl, it will have small pupils. if itsa boy, it will have large pupils.
i don't know if it is a boy or a girl
It can be either way, a girl can tell a boy that she loves him or a boy can tell a girl that he loves her.
You can tell by the tail if the tail is short than its a girl if the tail is long its a boy!
You can tell whether or not your rabbit is a boy/girl by looking under its butt.
If you have a penis your probably is a boy.