Rationale: There is increasing interest in the potential influence of fetal and early life conditions on childhood wheezing. Objectives: To investigate the associations between maternal complications and procedures in pregnancy and at birth and the risk of various wheezing phenotypes in young children. Methods: We studied 15,609 children, aged 6-7 yr, enrolled in a population-based study. Standardized questionnaires were completed by the children's mothers. Results: Of the children, 9.5% (1,478) had transient early wheezing, 5.4% (884) had persistent wheezing, and 6.1% (948) had late-onset wheezing. Maternal hypertension or preeclampsia was associated with an increased risk of all three wheezing phenotypes (for transient early wheezing: odds ratio [OR], 1.40; 95% confidence interval [95% CI], 1.08-1.82; for persistent wheezing: OR, 1.59; 95% Cl, 1.15-2.19; and for late-onset wheezing: OR, 1.47; 95% Cl, 1.06-2.01). Use of antibiotics for urinary tract infections was associated with transient early wheezing (OR, 1.52; 95% Cl, 1.16-2.00), whereas antibiotic administration at delivery was associated with both transient early wheezing (OR, 1.21; 95% Cl, 1.01-1.46) and persistent wheezing (OR, 1.39; 95% Cl, 1.10-1.75). Children who had a mother with diabetes were also more likely to have persistent wheezing (OR, 1.72; 95% Cl, 0.99-3.00). Neither amniocentesis/ chorionic villus sampling, nor weight gain in pregnancy, nor cesarean section was associated with the subsequent development of wheezing. Maternal asthma or atopy was not an effect modifier of the associations found. Conclusions: Some maternal complications during pregnancy and at delivery may increase the risk of developing different phenotypes of wheezing in childhood.