( ( At ( ( about ( nine weeks ) ) ( into ( the pregnancy ) ) ) ) ( , ( ( the fetus ) ( ( begins ( to ( engage ( in ( movements ( that ( resemble breathing ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN At) (PP (NP (RB about) (CD nine) (NNS weeks)) (IN into) (NP (DT the) (NN pregnancy)))) (, ,) (NP (DT the) (NN fetus)) (VP (VBZ begins) (S (VP (TO to) (VP (VB engage) (PP (IN in) (NP (NP (NNS movements)) (SBAR (WHNP (WDT that)) (S (VP (VBP resemble) (S (VP (VBG breathing)))))))))))) (. .)))
At about nine weeks into the pregnancy, the fetus begins to engage in movements that resemble breathing.
(ROOT (S (NP (NP (DT The) (NN development)) (PP (IN of) (NP (NP (DT the) (JJ respiratory) (NN system)) (PP (IN in) (NP (DT the) (NN fetus)))))) (VP (VBZ begins) (PP (IN at) (NP (QP (RB about) (CD 4)) (NNS weeks)))) (. .)))
The development of the respiratory system in the fetus begins at about 4 weeks.