All types of fruits n veggies are beneficial in pregnancy . Grapes too are rich in vitamin c , a and antioxidants . But unwashed and unclean grapes have a high load of pesticides in them . So please ensure they are clean ( eg -use salt water to soak n clean them ) before consumption.
Remember moderation is the key . So consume all types of fruits and vegetables (unless you are diabetic) but in small portions .