The question below was submitted to www.yoatzot.org, Nishmat's Women's Health and Halacha (Jewish Law) website for the lay public.
"Are you allowed to pump breastmilk on Shabbat? Manual? Electric if it's on before Shabbat and stays on until Shabbat ends?"
This is a common question that can arise in a number of situations, such as illness of the mother or the baby that precludes direct nursing (e.g., if one member of the dyad is hospitalized). Pumping milk from the breast into a container (as opposed to the baby's mouth) for the purpose of using the milk is biblically prohibited on Shabbat. If the milk is discarded or made unfit for use, then there is a rabbinic prohibition. In cases of pain or illness, the halacha makes exceptions.
The answer to this question depends what the purpose of the pumping is. In cases of maternal illness (e.g., breast infection, engorgement), it would be permitted either to express the milk for discarding (e.g., straight into sink) or into a container with soap in it. When the milk is required to feed an infant who is ill, then an individual question must be asked. The ruling will depend on a number of factors, such as the infant's age and condition.
If milk expression is permitted in a given situation, it can be done via hand expression, use of a manual pump, or use of an electric pump on a timer. When using a timer, it is important that the breast be positioned within the flange of the pump before the timer activates the machine. In addition to ruining the motor, leaving the pump on for all of Shabbat increases the halachic difficulties because putting the breast on the pump starts the pumping process directly. This is halachically more problematic than setting the machine goes on automatically when the breast is already in position. An individual halachic question should be asked in each case.
It is important to remember that there are two purposes involved in breast milk expression. The first is to prevent pain and increased risk of infection on the part of the mother. For this purpose, some form of expression is always permitted, although the milk may have to be discarded or rendered unfit for use. The second purpose is for the child to obtain the milk. The answer to this will depend on the condition of the child and the availability of additional previously pumped milk. The physician can aid the breastfeeding mother in asking her halachic question by clearly explaining the importance of breast milk and the risks of substituting artificial milk. A good summary of the current scientific data can be found in: American Academy of Pediatrics. Breastfeeding and the use of human milk. Pediatrics 2005;115:496-506. This article can also be accessed via the AAP website (www.aap.org).
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