For instance, the risk of coronary heart disease increases with smoking or obesity. Maternal ingestion of valproic acid, a medication for seizures, increases the risk of spine bifida. Maternal alcohol abuse or uncontrolled diabetes increases the risk of having a child with a congenital heart defect. Empiric risks are used to predict the recurrence of a multifactorial disorder. This is a risk that is based on epidemiologic and population studies and on mathematical models.
Affected individuals have a similar risk in future progeny.
More distant relatives, however, have a lower recurrence risk. In conditions inherited in a multifactorial fashion, the risk may depend on the sex of the affected individual. For example, pyloric stenosis is a multifactorial disorder that occurs five times more frequently in males than in females. If a female child has pyloric stenosis, her risk and her parent's risk of having another affected child would be higher than if a male child has pyloric stenosis. The greater the number of affected relatives, the higher the recurrence risk.