Institutional Birth (IB): includes all deliveries that occurred at a health facility. Lee S-I, Khang Y-H, Yun S, Joa M-W. Rising rates, changing relationships: caesarean section and its correlates in South Korea, 1988–2000. BJOG. 2005;112:810-9. doi: 10.1111/j.1471-0528.2004.00535.x.