Small. Pvl is more common in premature than term infants, and occurs more frequently with decreasing gestational age and size. Study showed the incidence of pvl is ~ 3-4% of infants who weigh < 1, 500 g (3.3 lb) have pvl, and 4-10% of those born < 33 weeks of gestation (but who survive more than three days postpartum). Another suggest <32 weeks account for~2% of all live births in usa.
Low. Pvl, or periventricular leukomalacia, is a condition where "water-shed" areas in the brain suffer ischemic injury leading to loss of brain tissue. Pvl is most often described in extremely premature (< 28 wk gestation) infants, but the exact cause is unknown. Although less premature infants may develop pvl, this is very uncommon, and is usually preceded by a profound hypoxic or inflammatory event.