Some disorders are caused by external or environmental factors, such as viral infections, medicines, and alcohol that harm the unborn baby; they are not hereditary.
Ezinye iingxaki zibangelwa ziimeko zangaphandle okanye kokusingqongileyo njengosuleleko lwentsholongwane, amayeza kunye notywala obonzakalisa usana olungekazalwa; yaye zona azinanto yakwenza nofuzo.