Fasting During Pregnancy: What to Tell a Patient Before Yom Kippur
Pregnant women often ask if they can fast on Yom Kippur. The answer is not a simple yes or no—it’s a conversation at the crossroads of medicine, faith, and ethics.
The week before Yom Kippur, the holiest day of the Jewish year, a 28-week pregnant patient came to see me. She is Jewish, and every year since adulthood she has fasted on Yom Kippur, the Day of Atonement. She looked at me and asked a simple but profound question: “Doctor, can I fast this year?”
It is not just a medical question. It is also religious, cultural, and ethical. And like so much in obstetrics, the right answer is not a single “yes” or “no” but a careful balancing act.
The Rules of Yom Kippur Fasting
For observant Jews, Yom Kippur begins at sunset on October 1 this year. The fast lasts about 25 hours: no food and no drink, not even water. It is considered the holiest day in the Jewish calendar, a day of reflection, prayer, and repentance.
But what does fasting really mean? Traditionally, it means complete abstinence from both food and drink. However, in medical terms, we often distinguish between fasting without food and fasting without fluids. The body tolerates a short period without calories far better than it tolerates dehydration. Pregnant women, especially, are more vulnerable to fluid loss, which can trigger contractions, dizziness, and stress on the fetus.
Jewish law (halacha) does recognize exceptions. Life and health come before fasting. Pregnant women, breastfeeding women, children, and the ill are explicitly considered differently. Many rabbis will counsel that if fasting threatens maternal or fetal health, one should eat or drink, ideally in small amounts spaced apart.
What We Know Medically
The medical literature on short-term religious fasting during pregnancy is surprisingly thin.
Ramadan studies: Most research comes from Muslim women fasting during Ramadan, often daily from sunrise to sunset for a month. Findings are mixed. Some studies show no major effects on birthweight or outcomes. Others suggest small but real risks: reduced amniotic fluid, increased ketones, and higher rates of preterm contractions.
Ketosis: After 12–18 hours without food, pregnant women tend to develop ketosis faster than non-pregnant women. High ketone levels may stress the fetus.
Dehydration: No fluid intake for 25 hours raises the risk of dehydration, especially in hot weather. Dehydration is linked to uterine contractions and even preterm labor.
Individual risk matters: Women with diabetes, hypertension, twins, growth-restricted fetuses, or a history of preterm labor are at higher risk. For them, fasting is strongly discouraged.
Evidence from Israel
Several studies conducted in Israel, where many pregnant women fast on Yom Kippur, have added to our understanding.
Researchers observed a higher incidence of women presenting to labor and delivery with contractions during or shortly after the fast. In some reports, up to double the usual number of women came in with signs of preterm or term labor compared with non-fasting days.
The mechanism appears to be dehydration, which reduces blood volume and can stimulate the release of oxytocin and prostaglandins, triggering uterine contractions.
Importantly, while more women went into labor or required evaluation, most pregnancies did not end in serious complications. The risks are real but typically reversible with hydration and rest.
Sergienko R, Glasser S, Shoham-Vardi I, Sergienko E, Sheiner E. The effect of Yom Kippur fast on pregnancy outcome. J Obstet Gynaecol. 2014;34(3):223-5. doi:10.3109/01443615.2013.853797.
Levy A, Fraser D, Katz M, Mazor M, Sheiner E. Fasting, fluid abstention, and labour outcome—a prospective study. Eur J Obstet Gynecol Reprod Biol. 2005;118(2):173-6. doi:10.1016/j.ejogrb.2004.03.041.
These findings reinforce what many of us see clinically: prolonged fasting without fluids potentially stresses the maternal-fetal unit and increases the chance of preterm contractions.
The Ethical Layer
This is where medicine and ethics intersect.
The ethical principle of autonomy means the patient ultimately decides. But beneficence (doing good) and non-maleficence (avoiding harm) mean I must clearly explain the risks, not minimize them, and help her make an informed choice.
There is also the principle of respect for culture and religion. Pregnancy is not just a medical condition, it is lived inside a family and community. For many, fasting on Yom Kippur is not optional—it is an expression of identity and spirituality. Simply saying “don’t fast” may not be helpful and may even be harmful to her sense of self.
A Relatable Analogy
I often tell patients: pregnancy is like training for a marathon with another person’s life depending on your hydration and energy. Running without water for 25 hours is not recommended. But adjusting your pace, sipping when needed, and recognizing warning signs keeps both you and the “teammate” safe.
Compensation for Not Fasting
Jewish law recognizes that fasting on Yom Kippur is a biblical obligation, but it also places the preservation of health and life above nearly all other commandments (pikuach nefesh). A pregnant woman who, upon medical and rabbinic guidance, does not complete the fast is not considered sinful and does not need to “make up” the fast on another day, since Yom Kippur is unique and cannot be postponed or repeated.
Instead, tradition emphasizes the triad of teshuvah (repentance), tefillah (prayer), and tzedakah (charity) as central expressions of Yom Kippur observance. Many rabbinic authorities recommend that women who are unable to fast, particularly those pregnant or breastfeeding, may enhance their observance by giving extra charity or providing food for the poor. One might note, with some scholarly irony, that Judaism long anticipated what social scientists call “compensatory practices,” in which an obligation unmet in one domain is balanced by increased commitment in another. This is not a commodification of observance, but rather an acknowledgement that spiritual integrity can be maintained through alternative forms of devotion and social responsibility.
Practical Guidance for Patients
What do I usually advise?
Talk with both your doctor and your rabbi. Jewish law allows exemptions, and medical input helps religious leaders give tailored guidance.
Assess your risk. High-risk pregnancy? Do not fast. Low-risk? It may be possible, but with caution.
Consider “partial” fasting. Some rabbis recommend eating or drinking minimal amounts at intervals (known as shiurim) rather than fully breaking the fast.
Prioritize fluids. Dehydration is often the biggest problem. Small sips of water throughout the day can make a major difference.
Recognize red flags. Dizziness, decreased fetal movement, uterine contractions, or signs of preterm labor mean you should stop the fast immediately and hydrate.
Plan ahead. Rest during the day, avoid hot environments, and prepare to resume hydration and nutrition as soon as the fast ends.
What Happened Next
After our discussion, my patient went to her rabbi. He told her:
“You may drink a glass of water every hour and regularly have small snacks. If you feel thirsty, drink more fluids. Your health and the baby’s health come first.”
This was a wise compromise. She could still observe the day in a meaningful way, but in a manner that prioritized safety. It was an example of medicine and religion working hand in hand.
What I Told My Patient
I told her:
“You are 28 weeks and otherwise healthy. The risks of one 25-hour complete fast are probably low, but they are not zero. By following your rabbi’s guidance—hydrating regularly and eating small amounts—you greatly reduce those risks. And if you feel unwell or notice less movement, you must stop fasting immediately. My role is to keep both you and your baby safe.”
She nodded. She felt respected in her faith and cared for in her pregnancy. And that is the goal.
Reflection
Pregnancy challenges our simple rules. What seems like a straightforward religious duty collides with the biology of a shared body. The ethical obligation of the physician is not to dictate, but to guide—firmly, compassionately, and with cultural respect.
So here is the question for all of us, physicians and readers alike: When health and faith meet at the bedside, how do we weigh tradition against safety, and who gets the final say?