Umbilical cord plasma erythropoietin levels in pregnancies complicated by maternal smoking

Objective: Our goal was to determine whether maternal smoking was associated with elevated umbilical cord erythropoietin, a marker for chronic hypoxia. Study Design: Plasma erythropoietin levels were measured in umbilical cord plasma of 222 newborns. There were 48 mothers who smoked and 174 nonsmokers. Results: When all pregnancies were included, mean cord plasma erythropoietin levels were significantly higher in the smokers (78.0 ± 15.3 mIU/ml) compared with the nonsmoking group (35.2 ± 4.0 mIU/ml; p< 0.005). Regression analysis showed a significant positive correlation between the number of cigarettes smoked per day and cord plasma erythropoietin levels (r = 0.26, p< 0.0001). Smoking was associated with a significantly elevated risk (relative risk = 2.6, 95% confidence interval 1.7 to 10.9, p< 0.005) of fetal growth restriction. When pregnancies with fetal growth restriction were excluded from the analysis, the difference between the two groups remained significant (smokers 81.3 ± 18.6, n = 38; nonsmokers 24.3 ± 1.4, n = 164; p< 0.03). Conclusions: These results illustrate that smoking during pregnancy is associated with fetal growth restriction and significantly elevated umbilical cord erythropoietin levels. (Am J Obstet Gynecol 1998;178: 433-5.)