Interpreting the carboxyhaemoglobin concentration in fetal cord blood.
We calculated the fetal-to-maternal carboxyhaemoglobin concentration ratio in 19 mother-infant pairs at the time of term delivery. Mothers, who had a less than 10% drop in their carboxyhaemoglobin concentration during labour, had an average ratio of 1.40 +/- 0.19. For mothers whose carboxyhaemoglobin concentrations dropped by 10% or more during labour, the average fetal-to-maternal carboxyhaemoglobin concentration ratio was 1.83 +/- 0.48. There was a strong correlation (r = 0.82) between the percent change in maternal carboxyhaemoglobin concentration during labour and the fetal-to-maternal carboxyhaemoglobin concentration ratio at the time of delivery. We conclude that increased CO elimination during labour may be accompanied by rapid changes in the maternal carboxyhaemoglobin concentration, leading to a spuriously high fetal-to-maternal carboxyhemoglobin concentration ratio at the time of delivery.
Department of Pediatrics, Stanford University School of Medicine, California 94305.
M B
MB
Leonard
H J
HJ
Vreman
J E
JE
Ferguson
D W
DW
Smith
D K
DK
Stevenson
D002248:Carbon Monoxide / Q000097:blood; D002263:Carboxyhemoglobin / Q000032:analysis*; D005260:Female; D005312:Fetal Blood / Q000032:analysis*; D006801:Humans; D006985:Hyperventilation / Q000150:complications; D007231:Infant, Newborn; D007743:Labor, Obstetric; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D012907:Smoking / Q000097:blood
D002248:Carbon Monoxide; D002263:Carboxyhemoglobin