Apostles didn’t mention it - see the Third Council of Ephesus - circa 431AD
http://www.newadvent.org/cathen/05491a.htm
AMDG
“But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.” Galatians 1:8-9
If the apostles didn't mention it why even consider what a bunch of guys wearing fish hats had to say 400 years later??? If Mary had been born sinless you can bet the apostles as well as Jesus would have had plenty to say about it...