It depends.
Article 258 defines who is a domestic as follows: Trabajadores dom?sticos son los que se dedican de modo exclusivo y en forma habitual y contin?a a labores de cocina, aseo, asistencia y dem?s, propias de un hogar o de otro sitio de residencia o habitaci?n particular, que no importen lucro o negocio para el empleador o sus parientes.
This means that nannies, just as as maids and gardeners, are considered domestics if they work at a home, and there is no business-related aspect to their work.