If the stenosis occurs late (eg, after 20 weeks), then the right ventricle has already developed, and the tricuspid valve becomes incompetent, the blood regurgitates, and the right atrium enlarges.

• 假如狭窄出现在晚期（比如孕20周后），这时右心室已经发育好了，三尖瓣就会发生功能不全，出现血液返流，右心房增大。