Rules of multifactorial inheritance
1.Recurrence risk is higher if more than one family member is affected.
2.The greater the severity, the higher the recurrence risk.
3.Recurrence risk is greater if the proband is of the less commonly affected gender.
4.Recurrence risk decreases rapidly in more distantly related individuals.
5.Recurrence risk for first degree relatives is approximately the square root of the population incidence of the trait.