Comparisons of mortality and pre-discharge respiratory outcomes in small-for-gestational-age and appropriate-for-gestational-age premature infants

Abstract

BackgroundThere are differences in the literature regarding outcomes of premature small-for-gestational-age (SGA) and appropriate-for gestational-age (AGA) infants, possibly due to failure to take into account gestational age at birth.ObjectiveTo compare mortality and respiratory morbidity of SGA and AGA premature newborn infants.Design/MethodsA retrospective study was done of the 2,487 infants born without congenital anomalies at ≤36 weeks of gestation and admitted to the neonatal intensive care unit (NICU) at John Dempsey Hospital, between Jan. 1992 and Dec. 1999. Recent (1994–96) U.S. birth weight percentiles for gestational age (GA), race and gender were used to classify neonates as SGA (<10th percentile for GA) or AGA (10th–90th percentile for GA). Using multivariate logistic regression and survival analyses to control for GA, SGA and AGA infants were compared for mortality and respiratory morbidity.ResultsControlling for GA, premature SGA infants were at a higher risk for mortality (Odds ratio 3.1, P = 0.001) and at lower risk of respiratory distress syndrome (OR = 0.71, p = 0.02) than AGA infants. However multivariate logistic regression modeling found that the odds of having respiratory distress syndrome (RDS) varied between SGA and AGA infants by GA. There was no change in RDS risk in SGA infants at GA ≤ 32 wk (OR = 1.27, 95% CI 0.32 – 1.98) but significantly decreased risk for RDS at GA > 32 wk (OR = 0.41, 95% CI 0.27 – 0.63; p < 0.01). After controlling for GA, SGA infants were observed to be at a significantly higher risk for developing chronic lung disease as compared to AGA infants (OR = 2.2, 95% CI = 1.2 – 3.9, P = 0.01). There was no significant difference between SGA and AGA infants in total days on ventilator. Among infants who survived, mean length of hospital stay was significantly higher in SGA infants born between 26–36 wks GA than AGA infants.ConclusionsPremature SGA infants have significantly higher mortality, significantly higher risk of developing chronic lung disease and longer hospital stay as compared to premature AGA infants. Even the reduced risk of RDS in infants born at ≥32 wk GA, (conferred possibly by intra-uterine stress leading to accelerated lung maturation) appears to be of transient effect and is counterbalanced by adverse effects of poor intrauterine growth on long term pulmonary outcomes such as chronic lung disease.

Ethnic differences in risk factors for neonatal mortality and morbidity in the neonatal intensive care unit

“…However, infants born SGA are at greater risk for mortality, neonatal morbidity and generally have longer lengths of stay than comparable infants of the same gestational age. 8 Furthermore, extreme prematurity (less than 29 weeks at birth) and outborn status have also been identified as strongly correlated with neonatal mortality in the NICU. 9 However, despite adjusting for these well-known predictors of mortality, South Asian race was still a significant indicator of infant mortality in our model.…”

Respiratory morbidity at follow-up of small-for-gestational-age infants born very prematurely

“…In the latter study (14), prenatal corticosteroid use was associated with decreased risks of both RDS and neonatal death. In none of the previous or the more recently reported studies (12)(13)(14), however, were infants routinely exposed to postnatal surfactant, and in the majority of studies, antenatal steroids were not routinely used. The aim of this study was to determine whether among infants born very prematurely, that is <29 wk of gestational age, who had been routinely exposed to both antenatal steroids and postnatal surfactant, neonatal and infant respiratory morbidity was increased in those who were born SGA.…”

“…Some studies have highlighted that small size at birth was associated with a reduction in the incidence of respiratory distress syndrome (RDS) (3,4), but other studies suggested no influence (5-9) or a significant increased risk (10,11). Subsequently, there have been three large studies (12)(13)(14) that demonstrated an association between being born small for gestational age (SGA) and an increased risk of respiratory morbidity. In a study of 2,487 infants born before 37 wk of gestation, SGA infants had a significantly greater risk of developing chronic lung disease or dying and had a longer hospital stay (12).…”

“…Subsequently, there have been three large studies (12)(13)(14) that demonstrated an association between being born small for gestational age (SGA) and an increased risk of respiratory morbidity. In a study of 2,487 infants born before 37 wk of gestation, SGA infants had a significantly greater risk of developing chronic lung disease or dying and had a longer hospital stay (12). In another series, which included 2,764 very low birth weight infants born between 24 and 31 wk of gestation, SGA infants had a 3.42-fold increased risk of bronchopulmonary dysplasia (BPD) and a 4.5-fold increased risk of death (13).…”

Association of newborn diseases with weight/length ratio and the adequacy of weight for gestational age

“…The greater frequency among NB with a low index is due to the fact that in this class there is a greater concentration of PT NB, as was previously described. On the other hand, among NB with low indexI there are also the FT SGA that would have some degree of protection against RDS by pulmonary maturity, favored by stress when this occurs after 32 weeks (17) . Kaplan et al reported that in NB with GA>36 weeks, the risk of presenting with RDS may vary from 1 to 39%, according to the surfactant/amniotic fluid (S/Af) ratio.…”