A limitation of this study is the cross- sectional design, which keeps from answering the question of question of causality. The prospective study of provided first evidence on the assumed causal direction that psychosocial problems predict continued smoking during pregnancy. Another limitation concerns the validity of self-reported smoking status, which is often unreliable and which in this study limited to early pregnancy . However, the actual associations are therefore probably even higher, because women with psychosocial problems usually are overrepresented among the group of false quitters.