When you are an employee, mothers have the right to 15 weeks of maternity leave (zwangerschapsverlof/congé de maternité), which are split up into 2 parts:
Prenatal leave before you give birth: 1 week is compulsory, 6 weeks is the maximum.
Postnatal leave beginning on the day of delivery: 9 weeks which are all compulsory.
If you only take up 1 week of prenatal leave you can transfer the remaining 5 weeks to the postnatal leave.
If your doctor tells you to rest due to complications and stay home in the time period of 6 weeks before the due date, your maternity leave will automatically start.
In case of a multiple pregnancy, maternity leave for employees is 17 weeks (8 prenatal, of which 1 compulsory; 9 weeks postnatal, all compulsory), but can be extended to 19 weeks.
Another reason you might get an extended leave is in case your newborn has to stay in the hospital for longer than 7 days after birth.
A freelance worker has the right to a maternity leave of 12 weeks, and 13 for multiples. https://www.mc.be/mes-avantages/naissance-enfance/naissance/conge/conge_maternite_independantes.jsp
https://www.vlaanderen.be/nl/werk/loopbaan/moederschapsverlof-en-moederschapsbescherming
Paternity leave: each worker is entitled to 10 days of paternity leave when your child is born. You can choose when you take these 10 days, but it must be within 4 months after the birth.
For more information in becoming a parent and working: http://www.emploi.belgique.be/publicationDefault.aspx?id=5572#