Harmony testing

So I am 22 and healthy and 11+4 with my rainbow baby. I want to get this test done but my insurance won't cover it unless there is a medical reason. The reason I want it is bc my sister had a baby that she had to terminate at 6 months due to anoplocephaly and turners syndrome and the dr said the baby had no chance at life. I told my dr this is she said the quad testing would be sufficient but you have to carry for a longer time and it will be harder if there is something wrong. How do I get my dr to agree to the harmony testing? I just want to know sooner so if that is something I may have to battle.