Poland sequence (sequence--geneticists' jargon for a bunch of things
occurring together) is unilateral defect of the pectoralis muscle and
syndactyly of hand (fingers partially or completely fused together).

Other things you can get are hypoplasia or absence of nipple and areola
on the same side as well as rib defects.  It may be due to diminished
blood supply to the area in utero.

Obviously if there is absent nipple and areola on the affected side,
breastfeeding on that side will not be possible.  But this does not
always occur, and just absence of the muscle will not cause
breastfeeding problems.  If this mother has absent or hypo (not hyper)
plastic breast on that side, she may produce less milk as well.

But, you can feed two with two, you can feed one with one.  I even have
one mother who fed two with one.

Jack Newman, MD, FRCPC