▁the ▁cause ▁in ▁over ▁ 9 5 % ▁of ▁cases . ▁Gen etic ▁testing ▁is ▁usually ▁carried ▁out ▁using ▁a ▁blood ▁sample , ▁and ▁ML PA ▁is ▁one ▁of ▁more ▁frequently ▁used ▁gen etic ▁testing ▁techniques , ▁as ▁it ▁also ▁allows ▁establish ing ▁the ▁number ▁of ▁SM N 2 ▁gene ▁copies . ▁ ▁Pre impl ant ation ▁testing ▁ ▁Pre impl ant ation ▁gen etic ▁diagn osis ▁can ▁be ▁used ▁to ▁screen ▁for ▁S MA - aff ected ▁emb ry os ▁during ▁in - v it ro ▁fert il isation . ▁ ▁P ren atal ▁testing ▁ ▁P ren atal ▁testing ▁for ▁S MA ▁is ▁possible ▁through ▁ch or ionic ▁vill us ▁sampling , ▁cell - free ▁f etal ▁DNA ▁analysis ▁and ▁other ▁methods . ▁ ▁Car rier ▁testing ▁ ▁Those ▁at ▁risk ▁of ▁being ▁carri ers ▁of ▁SM N 1 ▁delet ion , ▁and ▁thus ▁at ▁risk ▁of ▁having ▁off spring ▁affected ▁by ▁S MA , ▁can ▁under go ▁car rier ▁analysis ▁using ▁a ▁blood ▁or ▁sal iva ▁sample . ▁The ▁American ▁College ▁of ▁Ob st etr icians ▁and ▁Gy ne colog ists ▁recomm ends ▁all ▁people ▁thinking ▁of ▁becoming ▁pre gn ant ▁be ▁tested ▁to ▁see ▁if ▁they ▁are ▁a ▁car rier . ▁ ▁However , ▁gen etic ▁testing ▁will ▁not ▁be ▁able ▁to ▁identify ▁all ▁individuals ▁at ▁risk ▁since ▁about ▁ 2 % ▁of ▁cases ▁are ▁caused ▁by ▁de ▁nov o ▁mut ations ▁and ▁ 5 % ▁of ▁the ▁normal ▁populations ▁have ▁two ▁copies ▁of ▁SM N 1 ▁on ▁the