I was 36 when I gave birth to my 2nd son.
I only did IPS. My understranding is that
you need to do IPS first around 16 weeks.
Then, based on the result, I think there
are two ratios: Down-syndrome, and something else??. If your ratio (probability of having down-syndome) is far less than the threshold, then, you
are on the safer side. but not garanteed.
羊膜腔穿刺 is more accurate. You have to talk to your family doctor or OB, and your husband about the IPS result, the final decision is yours.
Happy pregancy and relax!