From the moment labor begins, or from the moment a woman must be rushed to the hospital to give birth, she is considered to be dangerously ill, and she must eat and drink as needed. She retains this status for seventy-two hours from the moment of birth. If these seventy-two hours end during Yom Kippur, she may eat and drink as needed until seventy-two hours have passed. As we have seen, it is preferable for anyone dangerously ill to eat and drink le-shi’urim if it will not be harmful. However, if a woman postpartum wants to sleep, and eating and drinking le-shi’urim will make it hard for her to get the rest she needs, then she should eat and drink normally.
From seventy-two hours until a week postpartum, her condition must be evaluated. If it is clear to her and her doctor that she is not at risk, she should fast. If they are uncertain, she should not fast (SA 617:4).