Association of fetal and maternal carboxyhemoglobin levels in normal and Rh-alloimmune pregnancies.
OBJECTIVE
To compare paired antepartum fetal/maternal COHb ratios in whole blood from control and alloimmunized pregnancies and to examine the relationships between fetal and maternal COHb.


METHODS
COHb levels were measured in paired fetal and maternal blood samples obtained at cordocentesis in 47 control and 16 Rh-alloimmunized pregnancies. COHb was determined by gas chromatography. Results were analyzed by t-test, regression and analysis of covariance.


RESULTS
Although fetal/maternal COHb ratios for control and alloimmunized pregnancies were not statistically significantly different, i.e. 1. 11+/-0.04 and 1.26+/-0.09, respectively (P=0.09), fetal COHb levels were higher in Rh-alloimmunized fetuses (P=0.0002). Fetal COHb levels were also higher than paired maternal levels among the alloimmunized group (P=0.011), but not among the control group (1. 04+/-0.04, P=ns). In univariate regression analysis, fetal and maternal COHb levels were significantly correlated with one another in both control (r=0.52, P=0.0002) and alloimmunized pregnancy groups (r=0.52, P=0.05). Comparison of the slopes of the fetal versus maternal COHb plots for the two groups showed a significant difference (P=0.02), with the alloimmunized group having the steeper slope.


CONCLUSIONS
Differences in the antepartum fetal-maternal COHb relationships in control and alloimmunized groups likely reflect increased endogenous CO production among alloimmunized fetuses as a result of pathologic hemolysis.
Department of Neonatology, University Children's Hospital, Waehringer Guertel 18-20, A1090, Vienna, Austria. haydmi1@vm.akh-wien.ac.at
M
M
Hayde
A
A
Pollak
G
G
Bernaschek
C P
CP
Weiner
H J
HJ
Vreman
D K
DK
Stevenson
J A
JA
Widness
D000328:Adult; D002263:Carboxyhemoglobin / Q000032:analysis*; D002849:Chromatography, Gas; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005313:Fetal Death; D005865:Gestational Age; D006801:Humans; D008297:Male; D011247:Pregnancy; D012044:Regression Analysis; D012203:Rh Isoimmunization / Q000097:blood*
D002263:Carboxyhemoglobin