( ( The ( active treatment ) ) ( ( should ( be ( ( ( ( preceded ( by ( a ( three ( week drug ) ) ) ) ) ( washout period ) ) and ) ( followed ( by ( ( a ( treatment phase ) ) ( lasting ( ( approximately six ) weeks ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ active) (NN treatment)) (VP (MD should) (VP (VB be) (VP (VP (VBN preceded) (PP (IN by) (NP (DT a) (CD three) (NN week) (NN drug))) (NP (JJ washout) (NN period))) (CC and) (VP (VBN followed) (PP (IN by) (NP (NP (DT a) (NN treatment) (NN phase)) (VP (VBG lasting) (NP (QP (RB approximately) (CD six)) (NNS weeks))))))))) (. .)))
The active treatment should be preceded by a three week drug washout period and followed by a treatment phase lasting approximately six weeks.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))