▁some ▁individuals ▁and ▁organizations ▁who ▁are ▁not ▁opposed ▁to ▁human ▁emb ry onic ▁stem ▁cell ▁research ▁to ▁be ▁concerned ▁about , ▁or ▁opposed ▁to , ▁SC NT ▁research . ▁ ▁One ▁concern ▁is ▁that ▁bl ast ula ▁creation ▁in ▁SC NT - based ▁human ▁stem ▁cell ▁research ▁will ▁lead ▁to ▁the ▁re product ive ▁cl oning ▁of ▁humans . ▁Both ▁processes ▁use ▁the ▁same ▁first ▁step : ▁the ▁creation ▁of ▁a ▁nuclear ▁transferred ▁emb ry o , ▁most ▁likely ▁via ▁SC NT . ▁Those ▁who ▁hold ▁this ▁concern ▁often ▁advoc ate ▁for ▁strong ▁reg ulation ▁of ▁SC NT ▁to ▁pre clude ▁impl ant ation ▁of ▁any ▁derived ▁products ▁for ▁the ▁intention ▁of ▁human ▁reprodu ction , ▁or ▁its ▁prohib ition . ▁ ▁A ▁second ▁important ▁concern ▁is ▁the ▁appropriate ▁source ▁of ▁the ▁eggs ▁that ▁are ▁needed . ▁SC NT ▁requires ▁human ▁egg ▁cells , ▁which ▁can ▁only ▁be ▁obtained ▁from ▁women . ▁The ▁most ▁common ▁source ▁of ▁these ▁eggs ▁today ▁are ▁eggs ▁that ▁are ▁produced ▁and ▁in ▁excess ▁of ▁the ▁clin ical ▁need ▁during ▁IV F ▁treatment . ▁This ▁is ▁a ▁minim ally ▁invas ive ▁procedure , ▁but ▁it ▁does ▁carry ▁some ▁health ▁ris ks , ▁such ▁as ▁o var ian ▁hyper st im ulation ▁synd rome . ▁ ▁One ▁vision ▁for ▁successful ▁stem ▁cell ▁ther ap ies ▁is ▁to ▁create ▁custom ▁stem ▁cell ▁lines ▁for ▁patients . ▁Each ▁custom ▁stem ▁cell ▁line ▁would ▁consist ▁of ▁a ▁collection ▁of ▁identical ▁stem ▁cells ▁each ▁carrying ▁the ▁patient ' s ▁own ▁DNA , ▁thus ▁reducing