Measuring placental transfusion for term births: weighing babies with cord intact

Abstract

Objective To estimate the volume and duration of placental transfusion at term.Design Prospective observational study.Setting Maternity unit in Bradford, UK.Population Twenty-six term births.Methods Babies were weighed with umbilical cord intact using digital scales that record an average weight every 2 seconds. Placental transfusion was calculated from the change in weight between birth and either cord clamping or when weighing stopped. Start and end weights were estimated using both a B-spline and inspection of graphs. Weight was converted to volume, 1 ml of blood weighing 1.05 g.Main outcome measures Volume and duration of placental transfusion.Results Twenty-six babies were weighed. Start weights were difficult to determine because of artefacts in the data as the baby was placed on the scales and wrapped. The mean difference in weight was 116 g [95% confidence interval (CI), 72-160 g] using the B-spline and 87 g (95% CI, 64-110 g) using inspection. Converting this to the mean volume of placental transfusion gave 110 ml (95% CI, 69-152 ml) and 83 ml (95% CI, 61-106 ml), respectively. Placental transfusion was usually complete by 2 minutes, but sometimes continued for up to 5 minutes. Based on the B-spline, placental transfusion contributed 32 ml (95% CI, 30-33 ml) per kilogram of birth weight to blood volume, but 24 ml (95% CI, 19-32 ml) based on inspection. This equates to 40% (95% CI, 37-42%) and 30% (24-40%), respectively, of total potential blood volume.Conclusion Inspection of the graphs probably underestimates placental transfusion. For term infants, placental transfusion contributes between one-third and one-quarter of total potential blood volume at birth.

Neonatal management and outcome in alloimmune hemolytic disease

“…In a term newborn, this transfusion can consist up to one-quarter to one-third of the total neonatal blood volume [65]. In anemia secondary to erythrocyte alloimmunization, a significant increase in hemoglobulin levels at birth was observed, as well as a longer delay between birth and first transfusion, and a decrease in the number of postnatal exchange transfusions, with no notable adverse effects [66,67].…”

Delayed umbilical cord clamping: potential for change in obstetric practice

“…1 They found that, for term birth, placental transfusion contributes between one-third and one-quarter of the neonatal blood volume. For most infants, placental transfusion appears to be complete by 2 minutes, but, for some, it continues for up to 5 minutes.…”

The Broader Implications of Early Cord Clamping at Birth.

“…The finding that depriving the neonate of a volume of blood [4] resulted in anaemia and iron deficiency six weeks later [5] was not surprising but only recently this anaemia and iron deficiency has been shown to have more significant long term adverse consequences [6]. While a reduction in fine motor skill is not trivial, it is unlikely to be life-threatening.…”

“…The original work of Yao [7] was repeated recently using accurate and recording electronic scales [4] and they showed that maximum volume of the placental transfusion can be at least 205 mls. By implication cord clamping within seconds of birth will prevent that volume of blood reaching the neonate.…”