( Measurements ( ( are ( taken ( at ( ( thirty ( ( -LRB- ( 30 -RRB- ) ) ( minute intervals ) ) ) ( for ( approximately ( two-week periods ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Measurements)) (VP (VBP are) (VP (VBN taken) (PP (IN at) (S (VP (VBG thirty) (NP (PRN (-LRB- -LRB-) (NP (CD 30)) (-RRB- -RRB-)) (JJ minute) (NNS intervals)) (PP (IN for) (NP (RB approximately) (JJ two-week) (NNS periods)))))))) (. .)))
Measurements are taken at thirty (30) minute intervals for approximately two-week periods.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))