Complications can include cardiac tamponade, myocarditis, and constrictive pericarditis. Chronic pericarditis however is less common, a form of which is constrictive pericarditis. The diagnosis of constrictive pericarditis is often difficult to make. A form of constrictive bronchiolitis is starting to present in Iraq and Afghanistan veterans. The name cryptogenic obliterative (constrictive) bronchiolitis is used when a cause is unknown. Underwire bras, like other constrictive garments, may contribute to clogged milk ducts in lactating women. OB can be further classified into two categories&colon; constrictive or proliferative. Breast binding is the act of flattening breasts by the use of constrictive materials. That particular restriction exemplified the increasingly constrictive, male-dominated medical community. Narrow steamboats were used to navigate the constrictive and winding river. However, population pyramids will be defined as the following&colon; stationary, expansive, or constrictive. Morsell in particular said she found it challenging because it was so physically constrictive. These two constrictive laws (natural and moral) are linked. This is compounded by an ageing demographic and a "constrictive pyramid" structure.