Typically, the chance of having a second baby with tetralogy of fallot is low, around 3%. Both environmental and genetic factors exist in the occurrence of ToF, so it is hard to predict ACTUAL risk of recurrence of ToF in your family. We know that mother's diabetes, or exposures to things like retinoic acid early in pregnancy, are linked to babies with ToF. Also, if your family members have DiGeorge's syndrome, the risk of Tof might be elevated.