Maternal smoking and fetal erythropoietin levels.

OBJECTIVE: To determine the influence of maternal smoking on fetal erythropoietin concentrations in health term pregnancies and test the correlation between cotinine, a biomarker of maternal smoking, and erythropoietin levels in fetuses.
METHODS: We invited women with healthy term pregnancies to participate in the study, excluding those with conditions previously known to be associated with elevated fetal erythropoietin levels. We recorded demographic data, smoking status, and labor outcome prospectively for each patient. Umbilical venous samples were collected, and serum was stored at -70C to be analyzed later for erythropoietin and cotinine. Umbilical arterial samples were tested for pH and base excess determination. We compared fetal erythropoietin and cotinine between smokers and nonsmokers and examined correlations between erythropoietin and cotinine. Kruskal-Wallis test, t test, median test, and Spearman rank correlation test were used when appropriate. Statistical significance was P <.05.
RESULTS: We recruited 35 nonsmokers and 26 smokers and analyzed their samples. The two groups were comparable in demographics and birth outcomes, except for birth weights, which were lower in smokers. Fetal erythropoietin concentrations increased significantly with increasing maternal cigarette consumption, ranging from none to more than 15 cigarettes per day (P =.03). There was positive correlation between fetal erythropoietin and cotinine concentrations (r =.41; P =.04), suggesting a dose-response relationship.
CONCLUSION: Fetuses of smokers had increased erythropoietin concentrations that correlate positively with fetal cotinine levels; which suggests an increased risk of subacute hypoxia related to degree of maternal cigarette consumption.