The following information is intended as an educational guideline for normal and healthy pregnancies. You should not rely on this information as a substitute for personal medical advice.
A pregnant woman should observe the fast normally, provided she and her baby are in good health. Nevertheless, if during Yom Kippur she feels sick (especially if she is vomiting or having other symptoms of dehydration) she should break the fast and eat immediately. However, mild dizziness and nausea that can be cope with by lying down on a couch or a bed, are considered normal, and should be endured.
Dr Jessica Jacob O.B. explains that according to research done on healthy pregnant women, there is no evidence that fasting would bring any complication to the mother or her baby. Three years ago, Dr J. Jacob gave a very detailed lecture in our community on 'Pregnancy and Yom Kippur'. I strongly recommend listening to her lecture where she explains the studies that were done on this subject. She also explains why would doctors typically advise a pregnant woman against fasting; how to cope with discomfort and in which circumstances a pregnant woman MUST break the fast, etc.
Click here to listen to Dr Jacob's lecture
For pregnant women and other cases
If you were instructed by your doctor to eat on Yom Kippur, and you don't need to eat a large amount of food or liquids at once, you should proceed as follows:
1. Eat a portion of food that weights less than 1 Oz. (1 ounce = 30 grams). After you finished the first portion you should wait ten minutes and eat a second portion, less than 1 Oz. . You could do this, until you recover.
2. For drinking, you should drink up to a little more than 1 Oz. Then, wait 5 minutes and drink 1 Oz. again, and so forth.
If possible, once you feel better, you should continue the fast.
To measure "1 ounce" it is advisable to use the plastic 1 Oz. liquor shot cups (Kiddush little plastic cups).