Apgar scores are used routinely to assess early neonatal status, but a
re less accurate in the preterm neonate because of developmental immat
urity. Attention has been directed to umbilical cord gases as a method
of neonatal evaluation. Using a retrospective chart review of all via
ble preterm births (24-36 weeks' gestation) between January 1986 and D
ecember 1989, we tabulated the umbilical cord gas indices of these inf
ants. Fetuses with lethal congenital anomalies and those with abnormal
heart rate tracings on admission were excluded from the data base, le
aving 1872 infants. Cord arterial blood gas values were available for
analysis in 74.4% of cases and cord venous gas values in 81.8%. The me
an (+/- standard deviation [SD]) arterial and venous umbilical cord bl
ood gas values for the preterm infants were, respectively: pH, 7.26 +/
- 0.08 and 7.33 +/- 0.07; oxygen pressure, 19.0 +/- 7.9 and 29.2 +/- 9
.7 mmHg; carbon dioxide pressure, 53.0 +/- 10.0 and 43.4 +/- 8.3 mmHg;
bicarbonate, 24.0 +/- 2.3 and 22.8 +/- 2.1 mEq/L; and base excess, -3
.2 +/- 2.9 and -2.6 +/- 2.5 mEq/L. Acidemia was defined statistically
as 2 SDs or more below the population mean. The incidence of 5-minute
Apgar scores below 7 in the preterm infants was 8.5% and within this g
roup, 17.8% were acidemic (arterial pH 7.10 or lower). More than 82% o
f neonates with 5-minute Apgar scores less than 7 had normal umbilical
cord blood gases. There was no significant difference in umbilical ar
terial blood gas values between preterm infants and 1924 term deliveri
es at our institution between 1986-1988. We conclude that there is no
significant difference in acid-base status at birth between the preter
m and term infant. Because umbilical cord gas indices are an objective
means of assessing the immediate status of the newborn, they may be o
f more value in excluding birth asphyxia than is the Apgar score for p
reterm infants.