In an earlier paper (Gairdner, Marks and Roscoe, 1952) we drew attention to the fact that the haemoglobin (Hb) level during the first day of life is generally much higher than at birth. We questioned the adequacy of the current explanation, that any rise in the Hb level after birth is the result of transfer of placental blood, and suggested that the effect merited study. We now present further observations comparing the composition of cord blood at birth with venous blood taken from a few minutes to a few hours after birth. Hb, packed cell volume, (PCV), plasma protein and plasma sodium have been measured. From these comparisons we conclude that after birth there is usually a shift of fluid, mainly whole plasma, from the circulation. The volume of the plasma shift may be large, amounting to an appreciable fraction of the initial plasma volume, and the effect may consequently prove to be of some clinical importance. MaterialNinety-two infants were studied, of whom 73 were delivered vaginally and 19 by caesarean section. The mother's permission for blood sampling was obtained. Most of the subjects were normal, but a few of the mothers had toxaemia or diabetes; the results in these were similar to those of the normals and have not been separately analysed. MethodsThe cord was always clamped as soon as conveniently possible, both in vaginal and caesarean deliveries. A blood sample was taken by puncture of the umbilical vein between placenta and clamp. Subsequent specimens were taken from an external jugular, internal jugular or femoral vein, or from the ductus venosus (i.e. the continuation of the umbilical vein). The ductus venosus was used particularly for samples within a few minutes of birth. We have found that the ductus venosus can often be catheterized conveniently by inserting a widebore trocar into the terminal part of the umbilical vein in the cord, and threading a polythene catheter through it.Samples were taken into heparinized tubes. Hb and PCV were estimated as described previously (Marks, Gairdner and Roscoe, 1955), Hb being estimated in duplicate in most cases. Plasma protein was estimated by the biuret method, using 0-2 ml. plasma. Plasma sodium was estimated by flame photometer. These four estimations required about 2 5 ml. of blood. Results(i) Change in Hb Level a Few Hours After Birth. In 92 infants samples were taken one to eight hours after birth and compared with cord blood. These included 19 caesarean deliveries, all but two of which were elective, and thus performed before the onset of labour. Results are shown in Fig. 1. Twenty-two cases showed a negligible change (less than ± 5 %) in Hb level after birth; in two cases there was a fall exceeding 5%, while the remaining 68 (74% of the sample) showed a rise exceeding 5 %. This rise amounted to 6-15% in 24 cases, to 16-25% in 23 cases, and to 26 % or over in 21 cases. In five cases the rise exceeded 40 %, the most extreme example being that of an infant born with an abnormally low haemoglobin level of 10i5 g./100 ml. which six hours after birt...

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A complete account of the changes in the blood picture in infancy requires a knowledge of the rates of formation and destruction of blood. Since the latter is not easily measured, our approach has been to use the activity of bone marrow as a measure of blood formation, and then to deduce whether changes in blood formation alone are sufficient to account for observed changes in the blood picture. Part I of the study, therefore, consists of an account of the marrow picture during the first three months of life. Part II concerns erythropoiesis, and the marrow findings are then considered together with the blood picture. Matenal and MethodsThe data to be discussed are derived from a total of 102 specimens of marrow from 25 infants aged from a few minutes to three months. A sample of venous blood was taken at the same time as the marrow.The infants were born in the Cambridge Maternity Hospital; the majority were chosen because their mothers had already borne a normal infant at the hospital and had volunteered to take part in the investigation; three subjects were mongols, but as their weight gains proved normal during the period under review, they were included in the series. Labour and delivery were normal, miniaial nitrous oxide and air anaesthesia being given to the mothers. Birth weights exceeded 6 lb. The cord was clamped as soon as conveniently possible, but usually some 10 to 15 seconds elapsed before this was done. Infants developing more than trivial infections were excluded. Sixteen of the 25 infants were completely breast fed. Weight gains were satisfactory and the infants generally were healthy and well cared for.

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