Influence of maternal cigarette smoking on maternal weight gain, uterine and umbilical flow velocities and fetal growth

Abstract

Objective: To investigate the effects of cigarette smoking during pregnancy on maternal body mass index, maternal weight gain, uterine and umbilical artery flow velocities and fetal growth.Methods: We studied 37 pregnant women (17 cigarette smokers [>10/day] and 20 non‐smokers) using an ATL HDI 5000 scanner for fetal anatomic survey and measurement of uterine and umbilical artery flow velocities. Maternal BMI change and weight gain during pregnancy, uterine and umbilical cord flow velocities, and fetal weight at delivery were measured in all patients.Results: There were no differences between the smoking and non‐smoking groups in gestational age at scanning (23.7 ± 1.5 vs. 26.5 ± 1.3 week), gravid (2.3 ± 0.3 vs. 2.1 ± 0.3) and parity (0.9 ± 0.2 vs. 0.6 ± 0.2). The median maternal BMI was less in smokers than non‐smokers both pre‐pregnancy (19 vs. 24) and at delivery (27.5 ± 1.3 vs. 32.3 ± 1.3). Maternal weight gain was less in smokers than non‐smokers (10.2 ± 1.6 vs. 14.7 ± 1.5 kg, P < 0.05). In the uterine artery, there was no significant difference in the systolic/diastolic ratio between smokers and non‐smokers (1.9 ± 0.1 vs. 1.8 ± 0.1). The umbilical artery systolic/diastolic ratio was greater in smokers than non‐smokers (3.25 ± 0.2 vs. 2.31 ± 0.07, P < 0.05) and fetal weight at delivery was lower in smokers (2.7 ± 0.2 vs. 3.3 ± 0.2 kg, P < 0.05).Conclusions: Decreased BMI and lower weight gain of women who smoke suggest that their nutritional intake may be lower than in non‐smokers. Decreased maternal weight gain in smokers and increased umbilico–placental resistance may both contribute to fetal growth restriction. Smoking appears not to affect utero‐placental resistance.