Strong's concordance indicates the original Greek word for child in this text is brephos and defined as: an unborn child, embryo, a foetus, a new-born child, an infant, a babe.
2 Timothy 3:15
ESV - 15 And how from childhood you have been acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.