( ( Week 4-8 ) ( ( is whan ) ( ( ( ( ( all ( the ( major ( organ systems ) ) ) ) ( of ( the body ) ) ) ( are formed ) ) and ) ( when ( ( most teratogens ) ( have ( their ( greatest effect ) ) ) ) ) ) ) )
(ROOT (S (NP (NNP Week) (NNP 4-8)) (VP (VBZ is) (ADJP (JJ whan)) (SBAR (SBAR (S (NP (NP (PDT all) (DT the) (JJ major) (NN organ) (NNS systems)) (PP (IN of) (NP (DT the) (NN body)))) (VP (VBP are) (VP (VBN formed))))) (CC and) (SBAR (WHADVP (WRB when)) (S (NP (JJS most) (NNS teratogens)) (VP (VBP have) (NP (PRP$ their) (JJS greatest) (NN effect)))))))))
Week 4-8 is whan all the major organ systems of the        body are formed and when most teratogens have their greatest        effect
(ROOT (S (PP (IN By) (NP (CD 8) (NNS weeks))) (, ,) (NP (DT all) (JJ major) (NNS organs)) (VP (VBP start) (S (VP (VBG developing)))) (. .)))