Had countless prenatal sonos. can congenital heart defect be undetected before birth?

Sure..: Unfortunately, the prenatal ultrasound detection rate for fetal cardiac defects is variable between 15-70% among centers, with the largest ones having the best results. As you can tell, short of having a fetal echo, the routine prenatal ultrasound (or even a comprehensive/targeted one) can miss even major cardiac defects in 30-85% of cases.. Take Folic Acid to prevent heart defects in you fetus!

Fetal : Yes if it is a Minor one or if it is a genetic arrhythmia syndrome