( ( For ( many years ) ) ( , ( lithium ( ( was ( thought ( to ( be ( ( the ( most teratogenic ) ) ( of ( these ( three medications ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (JJ many) (NNS years))) (, ,) (NP (NN lithium)) (VP (VBD was) (VP (VBN thought) (S (VP (TO to) (VP (VB be) (NP (NP (DT the) (JJS most) (NN teratogenic)) (PP (IN of) (NP (DT these) (CD three) (NNS medications))))))))) (. .)))
For many years, lithium was thought to be the most teratogenic of these three medications.
(ROOT (S (NP (NNP Lithium)) (VP (VBZ has) (NP (CD three) (NNS electrons))) (. .)))