Having a twin with ASD increases your baby's risk but does not guarantee it.
Genetic Factors
- Concordance: ~60–90% for identical (monozygotic) twins; ~10–30% for fraternal (dizygotic) twins.
- Hundreds of genes contribute; inheritance is polygenic, not Mendelian.
- De novo mutations also play a role.
Environmental Factors
- Advanced parental age
- Prenatal infections, maternal immune activation
- Prematurity, low birth weight, birth complications
- Prenatal valproate exposure
Key Points
- Risk is elevated but not deterministic.
- Each child's outcome is individual.
- Early monitoring and developmental screening are prudent.
- Genetic counseling provides personalized risk assessment.
Consult a geneticist or developmental pediatrician for family-specific guidance.
