Blood flow changes in the heart and lungs
			Apgar's newborn scoring system seems clearly associated with the vogue of   early clamping of the umbilical cord -- done with the aim of transferring the infant to a specialist and maintaining a sterile field for prompt suturing of incisions made for episiotomy or Caesarean delivery.  Meanwhile, advocates of what Apgar referred to as "slow birth" continued a long tradition of measuring the amount of placental blood an infant got if the cord was left unclamped until pulsations in it ceased.
				Pulsations continue as long as the valves in the infant's heart direct blood to the placenta through the umbilical arteries, and cease when pulmonary respiration is fully established with closure of the foramen ovale  and ductus arteriosus in the heart (Dawes et al. 1953).
		Changes in circulation through the heart and lungs were determined in newborn lambs.  These experiments did involve "tying the cord," which might explain the finding of a pattern of "neonatal circulation" intermediate between that of the fetus and that of the adult.  Born et al. (1954) found the ductus arteriosus begins to close within 5 to 15 minutes of pulmonary ventilation with continuing constriction for several minutes, but remained partially patent for 12 hours or more.  The foramen ovale, on the other hand, closes within a minute following birth, forcing circulation to the lungs.