In preterm infants, closure of the ductus arteriosus (DA) is often delayed, especially in those with respiratory distress syndrome (RDS). However, it has been suggested that functional closure of the DA may occur as early as 24 hours of age in some preterm infants exposed to intrauterine stress, and this is usually associated with decreased incidence of RDS. This suggests that accelerated maturation of the DA as well as of the lungs occurs in utero. Accordingly, histologic evidence of accelerated maturation of the DA was sought in a prospective autopsy study of 55 preterm infants ranging in gestational age from 19 to 32 weeks. There were four infants with clinically closed DA which showed histologic evidence of closure. The birth weight of these four infants ranged from 750--1,100 gm, the gestational age ranged from 24--32 weeks, and age of death was 39 hours to 6 days. The immediate causes of death were intracerebral hemorrhage or intrapulmonary hemorrhage, or both. Obstetric complications included chronic second trimester vaginal bleeding, abruptio placenta, malnutrition, diabetes, pulmonic stenosis of moderate degree, and chronic hypertension. These findings support the hypothesis that in some preterm infants exposed to chronic intrauterine stress, maturation of the DA is accelerated. This may result clinically in effective postnatal closure of the DA.
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