[Avodah] Fasting on YK

[Meir Shinnar]

In a discussion on areivim about pregnant women fasting on yom  
kippur, the issue was raised about the tension between classical psak  
(SA- ubrot umeinkot mitanot umashlimot beyom hakipurrim), and the  
opinion of most obstetricians today (note: while I am a physician, I  
am not an obstetrician), who believe that there is a risk in  
fasting.  There is also a tension between the statistical data from  
studies that there is an increased risk of fasting, and the  
dehydration that ensues, causing a women to deliver - both on time  
and early, and the experience of individual rabbanim who have not  
experienced a problem with their kehillot.  This reflects a more  
general issue of the nature of data that should be used in psak,  
especially in medical problems. Current medical practice (in all  
fields) is to view that the individual experience of even experienced  
practitioners can be skewed, and a more accurate reflection of  
reality is obtained by larger scale studies - and significant (both  
in a statistical sense and in clinical sense) differences can easily  
have been missed in the past.

As a continuation of that discussion, shunted by our moderators to  
avodah:

There are several separate issues that this raises.

1) What is the level of risk, and nature of risk, that is halachically
acceptable in this context?  Is it merely risk to the mother, or also
risk to the fetus? How machmir are we on pikuach nefesh?

2) Part of the issue that the halacha implies that there are pregnant
women for whom fasting either poses no risk, or else that the risks
for these women are within halachically acceptable bounds - and
indeed, that this is the norm for most pregnant women who are not
obviously sick.  Part of the issue is the extent to which this psak  
of the Shulchan Aruch - that it is safe for most pregnant women to  
fast - is viewed as an intrinsic psak, or merely reflecting the best  
medical practice of their time.  There is also now an intrinsic  
tension between two parts of standard psak - that most pregnant women  
should fast, and that for a pregnant woman, one listens to her  
phsyician, even non Jewish, about fasting....

Most obstetricians today would presumably (I am not an obstetrician)
argue that fasting poses some risks for all women.  As above, there is
statistical data on fasting increasing the delivery rate - as well as
mechanistic information to make this plausible.

Is it, therefore, halachically unreasonable to argue any of the
following positions:

1) Our current medical knowledge is such that we disagree with the
position that fasting is safe for most healthy pregnant women
(essentially a nishtanu hatevaim position - even if we mean by
nishtanu hatevaim that our knowledge is different (rabbenu avraham ben
harambam)
(In some ways, this is similar to the metziza debate - that current
medical knowledge would suggest the halacha is based on a medical
position that is no longer considered valid - but here there is the
problem of an issur karet, which makes it more difficult)

2)  While there may be a substantial population, or even the majority,
  of women for whom fasting in pregnancy may be safe, our current
status of medical knowledge does not allow us to determine who those
women are - we have learned enough to know that there is increased
risk for some, but not enough to identify more precisely the at risk  
population - and safek pikuach
nefesh lehakel...

3) While still recognizing that some women may still be safe fasting,
to dramatically limit the number of women who would be allowed to
fast (for example, healthy women who are already at term - and  
therefore delivering right after YK would not be problematic).


Meir Shinnar