The effects of maternal smoking on fetal cranial development. Findings from routine midtrimester sonographic anomaly screening

The aim of this study was to assess the effect of continued smoking before and during pregnancy on mid-trimester fetal head development. A total of 250 pregnant women enrolled in the study. All participants were confirmed to be smokers or non-smokers by verifying breath carbon monoxide readings. Biparietal diameter (BPD), head circumference (HC), lateral ventricle (LV), and cisterna magna (CM) were evaluated by ultrasound between 20-22 weeks of pregnancy. Gender and gestational age-adjusted BPD z- scores were not statistically different between smokers and non-smokers (-0.75 +/- 1.6 vs -0.51 +/- 1, p = .3). HC measurements and z- scores were significantly lower in the smoking group than in the non-smoking groups (183.38 +/- 14.56 vs. 189.28 +/- 12.53, p = .003, 0.18 +/- 1.39 multiple of median (MoM) vs. 0.56 +/- 0.92, respectively, p = .023). At linear regression analysis, maternal smoking was the only independent factor associated with fetal HC z score (p = .041). In conclusion, continued smoking during pregnancy reduces fetal HC and has no effect on BPD, LV, or CM measurements at mid-gestation. IMPACT STATEMENT What is already known on this subject? Smoking during pregnancy is one of the most common environmental factors affecting fetal and neonatal growth and well-being. Despite the well-known effects of smoking on somatic growth, current studies have shown that it selectively affects some parts of the fetal brain, even in appropriately growing fetuses. What do the results of this study add? Continued smoking during pregnancy reduces fetal HC and has no effect on BPD, LV or CM measurements at mid-gestation. Since smoking is well known for its early and late childhood behavioral and neurological consequences, smaller mid-trimester fetal HC measurements should bring maternal smoking to mind as one of the potentially reversible causes. What are the implications of these findings for clinical practice and/or further research? The harmful effects of smoking start before the third trimester and antenatal counseling should be started early in the gestation. Every effort should be made to quit smoking before or early in pregnancy.