Birth less than 37 weeks after conception. Infants born as early as 23–24 weeks may survive but many face lifelong disabilities (e.g., cerebral palsy, blindness, deafness). Premature infants account for 8–9percnt of live births but two-thirds of infant deaths. 40–50percnt of cases have no explanation; other cases can be attributed to such causes as maternal hypertension or diabetes, multiple pregnancy, or placental separation. With good care, about 85percnt of live-born premature infants should survive. Infants born very early (before 32–34 weeks) lack fully developed lungs and often develop respiratory distress syndrome. They also have problems maintaining body temperature and fighting infection. Most deaths result from breathing problems, infections, and brain or lung hemorrhages. Premature infants are characterized by low birth weight, small size, irregular breathing, absence of subcutaneous fat, and thin skin.

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