( ( If ( ( the placenta ) ( is ( expelled ( by ( 12 ( hours postpartum ) ) ) ) ) ) ) ( , ( ( the calving ) ( ( is ( considered normal ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT the) (NN placenta)) (VP (VBZ is) (VP (VBN expelled) (PP (IN by) (NP (CD 12) (NNS hours) (NN postpartum))))))) (, ,) (NP (DT the) (NN calving)) (VP (VBZ is) (VP (VBN considered) (S (ADJP (JJ normal))))) (. .)))
If the placenta is expelled by 12 hours postpartum, the calving is considered normal.
(ROOT (S (S (NP (DT The) (NN postpartum) (NN period)) (VP (VBZ starts) (SBAR (IN after) (S (NP (DT the) (NN baby)) (VP (VBZ is) (VP (VBN born))))))) (, ,) (CC and) (S (NP (DT the) (NN placenta)) (VP (VBZ is) (VP (VBN expelled) (PP (IN from) (NP (DT the) (NN body)))))) (. .)))