565. Premature Infants

Editor's note: The Rambam lived in the 12th century, so the following halachos may not be consistent with our current medical understanding. Please consult your own rabbi with any questions of practical application.

Milah 1:13

If a baby is born in the eighth month and his nails and hair are completely formed, we assume that this is a fully-developed baby that should have been born in the seventh month but was delayed. In such a case, the baby may be carried on Shabbos and may be circumcised on Shabbos. If the baby’s hair and nails were not completely formed, this is a child of the eighth month; he should not have been born until the ninth month but he came prematurely. Such a baby was not expected to survive and was not permitted to be moved on Shabbos. Once such a baby survived for thirty days, he is considered viable and is treated like any other infant.

Milah 1:14

If a baby is born in the seventh month and his limbs are completely formed, we assume that he will survive and the bris should be held on the eighth day (even if it’s Shabbos). If there is a doubt as to whether a baby was born in the seventh or eighth month, he may be circumcised on Shabbos. If he was born in the seventh month and his limbs are fully formed, the bris is supposed to override Shabbos; if he was born in the eighth month, circumcising him is halachically like cutting meat, since he is not considered viable.