Effects of intrauterine growth retardation and prematurity on spirometric flow values and lung volumes at school age in twin pairs

Abstract

Lung volumes and pulmonary expiratory flow values were investigated in 67 children from multiple pregnancies (30 twins, one set of triplets, one set of quadruplets) at the age of 7-15 years. At birth, 30 of 67 children (44%) had intrauterine growth retardation (IUGR, birth weight <-2 SD or birth weight difference between twin-pairs >1.3 SD). The median gestational age was 35 weeks (range, 28-38 weeks), and the median birth weight was 2,050 g (800-3,150 g). Lung functions were measured with a heated pneumotachograph. Data were standardized using height-based reference equations. No differences were found in lung volumes between children with IUGR and those children who had normal birth weight. Gestational age did not correlate with either airway flow rates or lung volumes. Maximum mid-expiratory flow (FEF50) did not correlate with standardized birth weight or with gestational age. In discordant twin pairs, the IUGR twins had significantly lower FEF50 than their normal birth weight counterparts (p=0.03, Z=-2.13). In the whole study group (67 children), children with IUGR had significantly lower FEF50 than children with normal birth weight (p=0.04; CI, 0.3-19.9). We propose that IUGR has the most pronounced effect on the growth of airways, and no detectable influence on lung volumes. This study confirms the crucial effect of appropriate intrauterine growth on subsequent growth on pulmonary airways.