Background: Maternal smoking during pregnancy is associated with a reduction in birth size. Very few studies have collated changes in fetal biometry, neonatal anthropometry, biochemical factors involved in fetal growth and measures of uterine and umbilical blood flow.

Methods: We related smoking status in 1650 low-risk, singleton Caucasian pregnancies delivering at term to measures of fetal growth, uterine and umbilical artery blood flow, placental appearance, birth size and cord concentrations of insulin-like growth factors (IGF) -1 and -2 and IGF binding protein (IGFBP) -3.

Results: Mothers who smoked in pregnancy were younger (P < 0.001), shorter (P = 0.03) and from lower socio-economic groups (P < 0.001). Mean umbilical artery blood flow at 20 weeks gestation was not associated with smoking status but was significantly higher in smokers at 30 weeks(P = 0.006). Uterine artery blood flow was unaffected. Smoking was associated with an increase in the percentage of abnormal placentas in a dose dependent manner and with a 3.1 fold increased risk (OR 3.1 95%CI 1.3-7.6) of abnormal umbilical artery blood flow (P = 0.009). Smoking was associated with a reduction in fetal femur length (P = 0.005) and abdominal circumference as well as birth weight, length and head circumference but not skinfold thickness. Cord plasma concentrations of IGF-1 and IGFBP-3 were lower in the babies of mother's who had smoked (P = 0.02 and P = 0.01 respectively).

Conclusion: Maternal smoking is associated with an altered placental appearance on ultrasonography, increased umbilical artery blood flow resistance and a reduction in longitudinal and intra-abdominal organ growth. Circulating concentrations of IGF-1 and IGFBP-3 are reduced along with measures of birth size but not markers of body fat suggesting smoking results in a reduction in organ size and function.