Joint Effect of Maternal Tobacco Smoking and Pregestational Diabetes on Preterm Births and Congenital Anomalies: A Population-Based Study in Northern Italy

Figure 1

Flowchart of the study population. 954 cases matched 5 controls, 66 cases matched 4 controls, 49 cases matched 3 controls, 31 cases matched 2 controls and 25 cases matched 1 control. 921 cases matched 5 controls, 22 cases matched 4 controls, 17 cases matched 3 controls, 12 cases matched 2 controls and 20 cases matched 1 control.