Is it permissible for a pregnant woman, whose fetus died in the beginning of the third month and from whom miscarriage bleeding occurred while she was fasting in Ramadan, to break her fast?

The blood a woman sees when she has a miscarriage before 81 days of pregnancy is not considered nifas (postnatal bleeding); rather, it is irregular bleeding. It is considered menstrual blood only if it coincides with the time of her usual monthly period; otherwise, it is irregular bleeding. You should fast and pray while seeing this blood, except for what coincides with the time of your usual period, in which case it is menstruation, and you should refrain from prayer and fasting.