( Measurements ( ( are ( taken ( at ( ( 30 ( minute intervals ) ) ( for ( ( approximately two ) ( week periods ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Measurements)) (VP (VBP are) (VP (VBN taken) (PP (IN at) (NP (NP (CD 30) (JJ minute) (NNS intervals)) (PP (IN for) (NP (QP (RB approximately) (CD two)) (NN week) (NNS periods))))))) (. .)))
Measurements are taken at 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)))) (. .)))