RESPIRATORY-FUNCTION AMONG PRETERM INFANTS WHOSE MOTHERS SMOKED DURING PREGNANCY

We examined whether the adverse effects of prenatal exposure to tobacc o on lung development are limited to the last weeks of gestation by co mparing respiratory function in preterm infants whose mothers had and had not smoked during pregnancy. Maximal forced expiratory flow ((V) o ver dot max(FRC)) and time to peak tidal expiratory flow as a proporti on of total expiratory time (T-PTEF:T-E) were measured prior to discha rge from hospital in 108 preterm infants (mean [SD] gestational age, 3 3.5 [1.8] wk), 40 of whose mothers had smoked during pregnancy. Infant urinary cotinine was less than 4 ng/ml in those born to nonsmokers, b ut it was as high as 458 ng/ml in exposed infants (p < 0.0001). T-PTEF :T-E was significantly lower in infants exposed to tobacco in utero (m ean [SD], 0.369 [0.109]) when compared with those who were not (0.426 [0.135]) (p less than or equal to 0.02). (V) over dot max(FRC) was als o reduced in exposed infants (mean [SD], 85.2 [41.7] ml/s versus 103.8 [49.7] ml/s) (p = 0.07). After allowing for sex, ethnic group, body s ize, postnatal age, and socioeconomic status, TPTEF:JE remained signif icantly diminished in infants exposed prenatally to tobacco (p < 0.05) . Thus, impaired respiratory function is evident in infants born on av erage 7 wk prior to the expected delivery date, suggesting that the ad verse effects of prenatal exposure to tobacco are not limited to the l ast week. of pregnancy.