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 woman in labor is exempted from fasting on Yom Kippur.
A pregnant woman, however, should observe the fast normally, provided she and the baby are in good health. Nevertheless, if during Yom Kippur she feels sick (especially if she is vomiting or having other signs of dehydration) she should break the fast and eat immediately (See below: how to eat). However, mild dizziness and nausea that can be coped with, by lying down on a couch or a bed, are considered normal, and should be endured.
If you were instructed by your doctor to eat on Yom Kippur you should do as follows:
1. Eat a portion of food that weights less than 1 oz. (an ounce is 30 grams). After you finished the first portion you should wait ten minutes and eat a second portion less than 1 oz. portion. You could do this, as many time as you need 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.
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).
When you eat or drink on Yom Kippur for medical reasons, you do not need to fast another day.
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'. It is highly recommended to listen to her lecture where she explains the studies that were done on this subject. She also explains why would a doctor advise a pregnant woman against fasting, how to cope with discomfort and when a pregnant woman MUST break the fast, etc.