There are two main scenarios to making Duas for down-syndrome. One, when the unborn is diagnosed with down-syndrome symptoms. Second, after the birth. According to my knowledge, there may not be a specific Dua for a condition but a series of Duas made at certain times. According to Ulama’ there is an hour every Friday that all the Duas asked to Allah S.W.A during that hour are answered.
I have consulted my Imam at the Masjid regarding this matter and will get back to you with more authentic information soon when I hear back from him, Insha’Allah.
IntelliAbb 
is there a dua for downsyndrome
Asslam-o-Alaikum Sister,
There are two main scenarios to making Duas for down-syndrome. One, when the unborn is diagnosed with down-syndrome symptoms. Second, after the birth. According to my knowledge, there may not be a specific Dua for a condition but a series of Duas made at certain times. According to Ulama’ there is an hour every Friday that all the Duas asked to Allah S.W.A during that hour are answered.
I have consulted my Imam at the Masjid regarding this matter and will get back to you with more authentic information soon when I hear back from him, Insha’Allah.
Jazak’Allah