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Hemoconcentration in smoking mothers is associated with impaired fetal growth
B Zarén1, G Lindmark, P Bergsjø
1Department of Obstetrics & Gynecology, University Hospital, Uppsala, Sweden.
Objective:
To examine the effect of maternal smoking on the relationship between maternal hemoglobin levels and pregnancy outcome.
Design:
A prospective study of healthy parous women from early pregnancy and of their infants.
Setting:
Three Scandinavian university hospitals covering all deliveries from well defined geographical areas.
Subjects:
Smoking (669) and non-smoking (368) mothers, para 1 and 2 and with > or = 37 weeks of gestational length.
Main Outcome Measures:
Birth weight and placental weight. Ponderal Index and Placental Index as measures of possible discordant fetal and placental growth.
Results:
In non-smoking mothers the hemoglobin levels in the three trimesters had no relation to birth weight. In smoking mothers a significantly lower birth weight was seen with a high hemoglobin level in the third trimester, but hemoglobin levels in early or mid-pregnancy had no association to birth weight. Smoking mothers also had a significantly greater fall in hemoglobin concentration from first to second and third trimester as compared to non-smokers although ferritin levels were similar in smokers and non-smokers, implying similar iron stores. The ratio of placental weight to the weight of the newborn was significantly higher in smokers, but no association was found to different hemoglobin levels.
Conclusions:
Fetal growth impairment associated with maternal smoking is even more pronounced in smoking mothers with high hemoglobin levels in late pregnancy. Smoking mothers were also found to have disproportional fetal/placental growth with relatively high placental weights. In non-smoking mothers hemoglobin levels had no relation to birthweight.