( ( ( About ( five weeks ) ) ( after ( ( your ( last period ) ) ( -LRB- ( ( ( three weeks ) ( after fertilization ) ) -RRB- ) ) ) ) ) ( , ( ( the ( fetal heart ) ) ( ( ( ( ( ( ( starts beating ) , ) and ) ( ( ( a week ) or ) ( so later ) ) ) , ) ( ( can first ) ( be ( seen ( by ( transvaginal ultrasound ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (NP (RB About) (CD five) (NNS weeks)) (IN after) (NP (NP (PRP$ your) (JJ last) (NN period)) (PRN (-LRB- -LRB-) (NP (NP (CD three) (NNS weeks)) (PP (IN after) (NP (NN fertilization)))) (-RRB- -RRB-)))) (, ,) (NP (DT the) (JJ fetal) (NN heart)) (VP (VP (VBZ starts) (NP (NN beating))) (, ,) (CC and) (ADVP (NP (DT a) (NN week)) (CC or) (ADVP (RB so) (RB later))) (, ,) (VP (MD can) (ADVP (RB first)) (VP (VB be) (VP (VBN seen) (PP (IN by) (NP (JJ transvaginal) (NN ultrasound))))))) (. .)))
About five weeks after your last period (three weeks after fertilization), the fetal heart starts beating, and a week or so later, can first be seen by transvaginal ultrasound.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))