My daughter, 21, may one day need surgery to replace regurgitation due to uneven mitral valve flaps after rhematic fev. At 7. Would that rule out preg?

No. Many women get pregnant after heart valve surgery. Often these women get a repair (with the right kind of problem and the right surgeon) or a pig-valve since they can often avoid the need for a blood thinner medication (warfarin). Even women on warfarin can get pregnant, but they need to plan with their doctor before pregnancy since the blood thinners need to be switched around.
Not necessarily. The problem with mitral valve surgery in rheumatic patients that are young is that they will likely receive a mechanical valve requiring warfarin/ coumadin( a bloodmthinner). These medications are known to cause birth defects and can be switched with another form of blood thinner if pregnancy is planned very carefully. It can be very complicated and risky for both mom and baby.