Webster's New World Medical Dictionary

preleukemia
See 
myelodysplastic syndrome.
premalignant
Pertaining to tissue that is not yet
malignant but is poised to become malignant.
Appropriate clinical and laboratory studies are
designed to detect premalignant tissue while it is
still in a premalignant stage. A battery of techniques
are available to remove or kill the tissue, thereby
preventing the development of cancer. The proper
treatment method depends on the particular prema-
lignant tissue involved. Examples of premalignant
growths include polyps in the colon, actinic kerato-
sis of the skin, dysplasia of the cervix, metaplasia of
the lung, and leukoplakia (white patches in the
mouth).
premature aging disorder
A condition that
causes a person to appear far older than their actual
age. See 
progeria; Werner syndrome.
premature baby
A baby who is born before 37
weeks of gestation have passed since the mother’s
last menstrual period. A premature baby who is
born very close to its due date may suffer few, if any,
consequences. The earlier in development that birth
takes place, the greater the likelihood that life-sup-
port systems will be needed and the greater the risk
for birth defects and death. Colloquially known as a
preemie. See also 
pregnancy; premature birth.
premature birth
Birth before 37 weeks of gesta-
tion have passed. Premature birth carries increased
risks the farther it occurs from the 37-week goal.
Many procedures are available to prevent prema-
ture birth, from bed rest to medications. If prema-
ture birth is medically necessary or inevitable,
however, it may be accomplished via C-section to
limit stress on the fetus. See also 
pregnancy; pre-
mature baby.
premature contraction of the heart
A single
heartbeat that occurs earlier than normal. This phe-
nomenon can be within normal limits, or it may
represent a medically significant arrhythmia.