The 80 percent figure comes from studies following autism in particular, but it is believed that the true stat is much higher (when factoring in birth defects and other diagnosis)

Reminds me of the stat that men are 6x more likely to leave their wife with cancer.

You have no control over whether or not your baby will be born with defects or develop special needs. You have no control over whether or not you'll develop cancer. You do have control over the partner you choose.

Before you have kids or even get married or even commit to a man that you may have kids with, you absolutely need to have a conversation about the possibility of having a special needs child. A lot of them will be straight up honest and point blank admit they would just leave. They'll find a pc way to phrase it, so you might have to read between the lines. But have that convo now and don't ignore your intuition.