B’Sha’ah Tovah!
Pregnant women are halachically obligated to
fast on Yom Kippur unless there is a specific cause for concern that fasting may be dangerous to the mother or fetus.
Given your specific situation, you are permitted eat and drink in
shiurim from the beginning of the fast. Please consult with your physician as to whether this will be sufficient and safe for you. It’s important for your doctor to be sensitive to the seriousness of the fast and give a well-thought-out answer.
Aside from that, you should make preparations to ease the fast as much as possible. Stay in bed all day in an air conditioned room. Arrange for help to take care of your other children. Your fasting takes precedence over your husband’s davening in shul, so if necessary he should daven in an early minyan, come home mid-morning to help you out, or even stay home altogether. Make sure to hydrate yourself very well for 2-3 days before the fast.
For future pregnancies a new question should be asked.
Please feel free to get back to us with any further questions.
Gmar chatimah tovah!