If one has rheumatic fever affecting the heart, will it cause lesser oxygenated blood to be pumped around the body?

There are many. potential cardiac issues that can occur with rheumatic heart disease. Some of these could potentially result in a decrease in effective oxygenation. This usually occurs as a late complication of untreated disease. See a health care provider to assess your situation and address your concerns.
Rheumatic heart . It's a valve disease so should not unless get hear failure .

Related Questions

When heart valves are slightly affected during rheumatic fever, can it still pump enough blood and nutrients around the body?

Many do. After the primary infection has resolved, the patient may do well. Damage is variable but also can evolve over time. A person may function quite well for years but end up needing a valve or valves replaced at some point in the future. Regular follow up with a heart specialist should be expected. Read more...