SUSTAINED ALTERATIONS IN POSTNATAL RESPIRATORY-FUNCTION FOLLOWING SUBOPTIMAL INTRAUTERINE CONDITIONS

This paper reviews recent evidence from epidemiological, follow-up and experimental studies that sub-optimal conditions during gestation can cause alterations in respiratory function that persist during postnat al life. Several studies indicate that placental insufficiency, which can be associated with fetal substrate deprivation, hypoxia and low bi rthweight, may be followed by evidence of respiratory compromise in la ter life. Similarly, it is becoming evident that maternal smoking affe cts fetal lung development and that the effects can persist into postn atal life. A reduced period of fetal development, due to preterm birth , may be associated with prolonged postnatal respiratory consequences which are independent of factors operating during the early postnatal period. Disorders of pregnancy that compress the fetal lungs, or that cause the abolition of fetal breathing movements, commonly lead to lun g hypoplasia. We have been interested in the prenatal causes and postn atal effects of fetal lung hypoplasia and have used an ovine model of rung hypoplasia induced by prolonged removal of amniotic fluid. This l eads to a reduction in the expansion of the fetal lungs which appears to be a common underlying cause of fetal lung hypoplasia. Studies of l ung function in lambs chronically exposed as fetuses to a lack of amni otic fluid showed that, although lung hypoplasia was apparently presen t throughout the 28-day postnatal study period, major alterations in r espiratory function were attributable to changes in chest wall complia nce. Thus, it is apparent that sub-optimal intrauterine conditions can have lasting effects on the structure and function of respiratory org ans. Available evidence indicates that the degree to which these organ s can recover postnatally may be restricted.