I am pregnant / nursing. Do I have to fast on Yom Kippur?
A woman after birth – up to and including the third day since birth – need not fast. Within seven days – consult with a Rov.
After that period of time- she must fast as normal, even though she might be feeling very weak.
The dispensation from fasting is only if it’s potentially a life threatening condition. Therefore, in low risk pregnancy, one should fast regularly unless accompanied by severe headaches, dehydration, dizziness etc.
It’s important to fast even at the expense of sleeping in bed all of Yom Kippur. Where practical, it’s important that husbands remain home instead of going to Shul to help their wife who is fasting.
If however one feels that their condition has deteriorated Chas V’sholom to the extent that it becomes a question of Sakana, then one can break their fast with Shiurim.
One can assess their health situation themselves. If they’re feeling very faint, they should break the fast using Shiurim. See the following for more information on Shiurim:
A woman in labor is permitted to eat and drink. However, whether it’s advisable medically to eat and drink during labor is a medical debate. Every individual should consult their own doctor.
See here for some general tips: