( ( At 8 ) ( weeks ( ( start AROM ) . ) ) )
(ROOT (S (PP (IN At) (NP (CD 8))) (NP (NNS weeks)) (VP (VBP start) (NP (NNP AROM))) (. .)))
At 8 weeks start AROM.
(ROOT (S (PP (IN By) (NP (CD 8) (NNS weeks))) (, ,) (NP (DT all) (JJ major) (NNS organs)) (VP (VBP start) (S (VP (VBG developing)))) (. .)))