( ( In humans ) ( , ( ( the ( fetal period ) ) ( ( begins ( at ( ( the ( eighth week ) ) ( of gestation ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NNS humans))) (, ,) (NP (DT the) (JJ fetal) (NN period)) (VP (VBZ begins) (PP (IN at) (NP (NP (DT the) (JJ eighth) (NN week)) (PP (IN of) (NP (NN gestation)))))) (. .)))
In humans, the fetal period begins at the eighth week of gestation.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))