Is it is a girl. a correct sentence?

The sentence, "Is it a girl?" or "It is a boy." seems awkward but English doesn't have a gender neutral third person singular pronoun. When the gender of a person is unknown, there is little choice but to use 'it'.

There is a great deal written about how to overcome this awkwardness. There is the "he or she", and "s/he", or alternating between "he" and "she" for a frequent occurrence in a text. No one is happy with any of these. Some suggest using 'he' or 'she' as a default when the gender is unknown but whichever one is chosen for default will be sexist to one group or another. One way to overcome the problem in many sentences is to reWord the sentence, "Is the baby a girl?" or "The baby is a boy." whenever possible.