B'Sha'ah Tovah!
The laws concerning Yom Kippur are strict and pregnant women are required to fast on Yom Kippur. Permission to eat is given in situations in which the fast is a threat to the woman's or fetus' health.
Even in the situation you describe, you should attempt to fast on Yom Kippur, being sure to hydrate yourself well during the two to three days beforehand and to get ample rest (lying down in a cool environment, arranging for help with the kids, etc). Your fast on Yom Kippur takes halachic precedence over your husband's davening in shul. He has a responsibility to help you get through the fast. Perhaps he can daven at an earlier minyan if you have one in your community, and come home for the rest of the morning to give you a break. You should also look into the possibility of hiring a babysitter. You should make it a priority to arrange such help in advance.
In general, if it gets to the point that you are feeling very nauseated or very weak or light headed despite lying down, you should begin to drink in
shiurim. The correct procedure is as follows:
You should drink less than one cheekful (
maleh logmav) at a time. The average cheekful is 40 ml, but you should measure your own mouth. Before Yom Kippur, fill up your mouth completely with water, then spit it into a cup and measure the quantity. Half of that is your
maleh logmav.
Ideally, you should wait nine minutes between drinks. If necessary, this can be reduced to five minutes or less. If you are sure you will have to drink, it is better to start earlier with
shiurim, rather than waiting to become dehydrated and having to drink more than a
shiur.
A more personalized ruling depends in part on your specific medical considerations. Therefore, you should consult with your physician prior to Yom Kippur for his or her opinions on the protocol above and the medical reasoning behind those opinions. (If you have access to a religious physician, that would be preferred.) Then you should get back to us or a local rabbinic authority with that information.
B'Hatzlacha!!
