Yom Kippur begins this Friday evening, September 17, and continues until Saturday evening. According to the Shulchan Aruch, the Code of Jewish Law, pregnant and nursing women are required to fast both on Yom Kippur (Day of Atonement ) and Tisha B’Av (9 Av, a day of mourning for the destruction of the Temple in Jerusalem).
Also see: Rabbi Elgazi on Breastfeeding, Pregnancy and Fasting on Yom Kippur (2012)
As I wrote in 2007 our local rabbi has ruled, based on Rabbi Nachum Rabinovich’s ruling, that nursing and pregnant women should not fast completely on those days. Instead, they should eat and drink shiurim beginning in the evening. According to Jewish law there is a minimum quantity, or shiur, or measurement that one must eat or drink in order to be breaking the fast. A person who eats less than this quantity within a specific time period is not fasting according to the strictest letter of the law. So in borderline cases this dispensation is often given.
The Nishmat website, which comes out strongly on the side of fasting for nursing and pregnant who have no complications, describes shiurim as follows:
The shiur for drinking is half of one mouthful (measured before the fast by filling the mouth and cheeks with liquid, emptying it into a measuring cup, and halving that). [MiI: 40 cc for me.] If eating is necessary, a woman may eat up to 30 cc at a time [MiI: one ounce]. Ideally, these quantities should be consumed at intervals of at least nine minutes; however, opinions vary and some authorities permit intervals as short as four minutes. A woman who needs to break her fast should have in mind while eating that she is fulfilling the mitzvah of “vechai bahem”, living for the sake of Torah (and not risking life).
I’ve heard that some women find a complete fast easier than eating or drinking shiurim, but I don’t believe that is a reason to avoid the leniency. The fluid—preferably juice and not water, for the extra calories—or food is clearly beneficial to the fetus or nursing baby, even if the mother senses no difference.
Rabbi Josh Waxman of Parshablog discusses the halachic basis of the ruling of Rabbi Rabinovich. A commenter wrote: “I think the real problem is the baseline assumption – mine is that without clear evidence, shomer psaim hashem kicks in. Every year, whole communities of women fast with no observed ill effect.”
This is a common claim, rejected by Rabbi Waxman:
I would have to disagree, though you are of course entitled to your opinion. What do you mean “no observed ill effect?” How could you know this? The only way you could know this is if you spun off another universe in which the women did not fast, and compared on a case by case basis to see that no woman had premature labor in our universe, and that the birth weight and fetal development was are the same. In fact, some portion of women do miscarry or have premature labor. And some infants have problems with development. Are these the result of fasting? I certainly do not know. But you certainly do not know either. However, studies performed on animals as well as on fasting pregnant women can assist in assessing that.
Rabbi Waxman, while not ruling one way or the other, provided links to studies that found concerns with fasting during pregnancy:
Source I: Metabolic Changes in Asian Muslim Women Pregnant Women Observing the Fast in Ramadan
1. Metabolic changes associated with Ramadan fasting were studied in eleven Asian pregnant mothers. This was compared with a group of control mothers undergoing a normal physiological fast.
2. At the end of the Ramadan fast day there was a significant fall in glucose, insulin, lactate and carnitine, and a rise in triglyceride, non-esterified fatty acid and 3-hydroxybutyrate. When compared with the control group, none of the Ramadan mothers had a completely normal set of biochemical values at the end of the fast day.
3. Pregnancy outcome in the two groups was comparable.
4. We are wary of the metabolic departures from normal observed in the Ramadan fasting mothers. If asked we advise mothers to take up the dispensation from fasting during pregnancy which is allowed.
Epidemiological evidence suggests that maternal psychosocial stress, strenuous physical activity and fasting are independent risk factors for preterm birth and low birth weight. Data from clinical studies consistently demonstrate that women in preterm labor have significantly elevated levels of corticotropin-releasing hormone compared with age-matched control subjects. Because production of corticotropin-releasing hormone appears to be stress sensitive, this neuropeptide may play a critical role in the physiological mediation among stressful experiences, work stress and fasting and risk of preterm birth. In addition to the direct effect of elevated corticotropin-releasing hormone on the initiation of labor, it may have an immunomodulatory effect such that women with high levels of corticotropin-releasing hormone may be more susceptible to infection or the pathological consequences of infection. We review the epidemiological data linking maternal stress, physical stain and fasting to preterm birth and low birth weight and review the plausible biological pathways through which these exposures may increase risk of preterm birth. The timing of these exposures is considered important. Future research and clinical programs addressing these exposures must consider assessments and interventions before pregnancy.
In studies in a rural West African village it was observed that all lactating women and 90 per cent of pregnant women fasted throughout the period of Ramadan. The metabolic consequences of this fasting were studied by measuring serum glucose, free fatty acid, triglyceride, beta-hydroxybutyrate, alanine, insulin, glucagon and T3 levels at 0700 h and 1900 h in 22 pregnant, 10 lactating and 10 non-pregnant, non-lactating women. Results were also compared with overnight-fasted values obtained outside Ramadan. Values for the lactating women were not significantly different from the non-pregnant, non-lactating controls despite the additional metabolic stress of lactation. Ramadan-fasted (1900 h) glucose values from women in late pregnancy (3.01 +/- 0.11 mmol/l) were significantly lower than all other groups (P less than 0.01) and were 15 per cent (P less than 0.01) lower than overnight-fasted values from similar subjects. Ramadan-fasted free fatty acid and beta-hydroxybutyrate levels were significantly higher (P less than 0.05) and alanine values were significantly lower (P less than 0.05) in late than in early pregnancy. It is concluded that the phenomenon of ‘accelerated starvation’ occurs when women in late pregnancy fast during Ramadan. The possible consequences of this failure to maintain glucose homoeostasis are discussed with reference to the poor outcome of the actual pregnancies studied.
Objective: Fasting during pregnancy stimulates preterm delivery in animals and increases women’s risk for preterm delivery. Fasting stimulates hypothalamic corticotropin-releasing hormone production in animals. Elevated maternal corticotropin-releasing hormone concentrations are associated with preterm birth. We hypothesized that prolonged periods without food during pregnancy increase maternal corticotropin-releasing hormone concentrations, which lead to preterm delivery.Study Design: In the Behavior in Pregnancy Study, we examined prolonged periods without eating during pregnancy and corticotropin-releasing hormone concentrations and gestational age at delivery with multivariate logistic regression analysis (n = 237).Results: Prolonged periods without food lasting 13 hours or longer were associated with elevated maternal corticotropin-releasing hormone concentrations compared with prolonged periods without food lasting less than 13 hours at two time points during pregnancy, controlling for pregravid body mass index, energy intake, income, race, smoking, and maternal age (18-20 weeks: adjusted odds ratio, 2.5; 95% CI, 0.9-7.1; 28-30 weeks: adjusted odds ratio, 1.7; 95% CI, 0.7-4.2). There was an inverse, linear relationship between maternal corticotropin-releasing hormone concentrations and gestational age at delivery.Conclusions: Prolonged periods without food intake during pregnancy are associated with elevated maternal corticotropin-releasing hormone concentrations and with preterm delivery. (Am J Obstet Gynecol 2001;185:403-12.)
The following two sources are more recent than Waxman’s post:
AbstractBACKGROUND: Placental growth responds to maternal influences. Ramadan is an annual period of day-time fasting during which people in Saudi Arabia, including pregnant women, change their diets and physical activity. Little is known about the effects of this altered lifestyle on placental development.
METHODS: We studied the birth records of 7083 babies born over a four-year period to Saudi nationals in Unizah, a small city 350 km to the north of Riyadh, the capital city of Saudi Arabia. The records included birth weight, placental weight and gestational age.
RESULTS: Mean birth weight was similar to European values but the mean placental weight and ratio of placental weight to birth weight were lower. Among babies who were in the second or third trimester of gestation during Ramadan the mean placental weight and ratio were below those of babies who were not in utero during Ramadan. Among boys the mean placental ratios were 14.4 percent (second trimester) and 14.5 percent (third trimester) compared with 14.9 percent (p=<0.001 and 0.002). The corresponding figures for girls were 14.8 and 14.6 percent compared with 15.1 percent (p=0.02 and <0.001).
CONCLUSIONS: In Saudi Arabia placentas respond to mothers’ limited ability to deliver nutrients to them. Placental growth slows but efficiency is increased so that fetal growth is sustained, albeit with a reduced reserve capacity. The lifestyle changes associated with Ramadan further slow placental growth. Ramadan may influence placental growth through dietary changes other than day-time fasting. Changes in placental growth during Ramadan could be associated with altered fetal programming, and may therefore have long-term implications for the health of the next generation.
A study by scientists in the United States, based on census data from the US, Iraq and Uganda, found that pregnant women who fast are likely to have smaller babies who are more prone to learning disabilities in adulthood.The researchers from Columbia University found that this trend was most marked if mothers-to-be fasted early on in their pregnancy and during the summer when longer days meant they went more hours without food.
I have not included the many studies that show no effect of fasting during pregnancy, according to the specific parameters measured in the individual studies.
Some of the studies involved fasting during Ramadan. The Ramadan fast is a month long, but only during daylight hours. The Yom Kippur fast only occur once, but for 25 hours straight. Any effect on the mother’s blood chemistry is greater. Another thing to keep in mind is that how well the mother feels is not necessarily an indicator of what is happening. A woman can fast well with no ill effects, but a related complication can occur later in pregnancy or after birth.
When discussing fasting with your rabbi, be sure to mention any difficulties you have had in your pregnancy or in previous pregnancies, or problems when fasting in the past.
A Radical Ruling: Fasting and Breastfeeding on Yom Kippur (includes information on why supplementing on YK is not always a good idea)