Down Syndrome is a genetically-transmitted disease cause by the presence of part or all of an extra 21st chromosome. We can’t blame this one on the drugs. However, drug use (including alcohol) while pregnant could complicate the issue with developmental problems.
I always remind people that if they use drugs during late-stage pregnancy, the child will be born with an addiction. Whether or not its later life is affected, the baby will have to withdraw from the drug during the first few days of life. Hell of a way to start your presence on the planet, wouldn’t you say?