The Effect of Smoking on Glucose Homeostasis and Fetal Growth in Pregnant Women

Objective: To examine the relationship between maternal blood glucose levels, cigarette smoking in pregnancy and fetal growth.

Design: A prospective study of healthy parous women from early pregnancy and their infants.

Setting: Three Scandinavian university hospitals covering all deliveries from well defined geographical areas.

Subjects: Study groups of non-smoking (150), light smoking (131) and heavily smoking mothers (218), para 1 and 2 and with > 37 weeks of gestational length.

Main Outcome Measures: Oral glucose tolerance test performed in pregnancy week 37, glycated hemoglobin measured the 3rd day post partum and neonatal anthropometric parameters including skinfold measurements.

Results: Among heavily smoking mothers 12.4% displayed a 2-hour glucose value in the range of gestational diabetes (> 8.5 mmol/l) compared to 9.2% among light smokers and 6.0% among nonsmokers (p < 0.05). Heavily smoking mothers also had significantly (p < 0.05) higher glycated hemoglobin compared to nonsmokers, 5.01 v.s. 4.86. These changes in glucose parameters in smokers were not associated with higher birthweights.

Conclusions: Smoking in pregnancy affects parameters of glucose homeostasis in the direction of gestational diabetes. The retarding effect of smoking on fetal growth abolished any expected growth stimulation from the higher blood glucose levels seen in the smokers.