( ( Statistical ( week 31 ) ) ( ( ( ( ( is , ) approximately ) , ) ( ( the ( last week ) ) ( in July ) ) ) . ) )
(ROOT (S (NP (NNP Statistical) (NN week) (CD 31)) (VP (VBZ is) (, ,) (ADVP (RB approximately)) (, ,) (NP (NP (DT the) (JJ last) (NN week)) (PP (IN in) (NP (NNP July))))) (. .)))
Statistical week 31 is, approximately, the last week in July.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))