In these situations the woman can abort the pregnancy before 40 days. Some scholars say before 120 days.
There are few articles on Islamonline and sunnipath with ahadith and fiqhi rulings.
A woman is allowed to abort the foetus in certain situations like
- Rape
- Incest
- Sexual interference with the mentally retarded
- Foetal deformity for e.g.. anencephaly (no brain)
- Foetal deformity for e.g.. congenital rubella health.