In terms of the health and wellbeing of the child, the general authority for child protection in Flanders is Kind en Gezin (Nationale Belgische Liga voor Kinderbescherming) they cover child care, parent support and adoption. https://www.kindengezin.be/algemeen/english-pages.jsp)
In the French speaking community this is covered by Office de la Naissance et de l’Enfance (ONE). (http://www.one.be/)
There are also organisations focused on the prevention and termination of child abuse.
In Flanders there are “vertrouwenscentrum kindermishandeling (VK), you can find the nearest on the following link:
http://www.kindermishandeling.be/website/11-www.html
In Wallonia you can contact the Equipes SOS Enfants.
http://www.one.be/index.php?id=2380
There is also a hotline you can call to report child abuse any working day between 9:00 and 17:00 on the number 1712, which is free.
In terms of safety, you can contact the police on the number 101 (or 100 or 112).
In case your child goes missing you can call Child Focus on 116 000.