Although several investigators have attempted to define the normal values of umbilical cord blood pH and gases, there is considerable controversy about the optimal cut offs values to diagnose intrapartum asphyxia. A possible reason for this might
be
that several studies have included data from fetuses born after different duration of labor. Therefore the normal values of umbilical cord arterial pH and gases that might be altered according to the effect of labor and duration of second stage
of
labor
were determined in 356 healthy term infants. Patients were divide into three group. A- patients delivered by cesarean section in the absence of labor (n=135). B-patients delivered by cesarean section during first stage of labor (n=62). C-
patients
with
vaginal birth (n=159), this group was subdivided according to the duration of second stage of labor: <30 min (n=91), 31~60 min (n=58), > 60 min (n=10). A Kruskal-Wallis ANOVA with post-hoc procedures and stepwise multiple regression analysis
among
the
study group indicated that there was a significant fall in umbilical arterial pH and bicarbonate with the presence of labor and increased duration of second stage of labor in health term neonate. It was confirmed by SAS Univariate program that
umbilical
cord arterial pH and bicarbonate showed normal distribution whereas pCO2 and pO2 didn't, The normal mean values ±standard deviations for umbilical cord aterial pH were: 7.275±0.052 in newborns delivered by cesarean sectio with epidural
anesthesia
in
the absence of labor, 7.260±0.049 in those delivered by cesarean section with epidural anesthesia during the first stage of labor, 7.290±0.049 in those delivered by cesarean section with general anesthesia during the first stage of labor,
7.252±0.071
in those born vaginally after second stage of labor lasting less than 30 minutes, 7.223±0.064 in those born vaginally after second stage of labor lasting 31 to 60 minutes, and 7.208±0.072 in those born vaginally after second stage of labor
lasting 31
to 60 minutes. The normal median value (5 percentile ~ 95 percentile) for umbilical cord arterial pCO2 values of which were not altered according to the effect of labor, duration of labor and type of anesthesia, was 50mmHg (32~65mmHg). The normal
median
values (5 percentile ~ 95 percentile) for umbilical cord arterial pO2 were 22mmHg (12~42mmHg) in newborns delivered by cesarean section with epidural anesthesia in the absence of labor, those delivered by cesarean section with epidural anesthesia
during
the first stage of labor and those born vaginally, but 30mmHg (21~40mmHg) in those delivered by cesarean section with general anesthesia during the first stage of labor. The normal mean values ± standard deviations for umbilical cord arterial
bicarbonate were 23.5±5.1 mEq/L in newborns delivered by cesarean section with epidural or general anesthesia 23.5±7.1 mEq/L in those delivered by cesarean section with epidural or general anesthesia during the first stage of labor 2.11±3.1
mEq/L in
newborns born vaginally after second stage of labor lasting less than 30 minutes, 2.01±5.9 mEq/L in those born vaginally after second stage of labor lasting 31 to 60 minutes, and 23.4±9.3 mEq/L in those born vaginally after second stag of labor
lasting longer than 61 minutes. These data suggest that the concerned labor-related factors, that is, the presence of labor and increased duration of second stage of labor should be taken into consideration in evaluating neonatal well-being by
cord
blood pH and acid-base measurements.
|