Advanced maternal age and the outcomes of preterm neonates: a social paradox?

OBJECTIVE: To estimate the effect of maternal age on survival free of major morbidity among preterm newborns younger than 33 weeks of gestation at birth. METHODS: Data from a retrospective cohort of preterm newborns younger than 33 weeks of gestation admitted to Canadian neonatal intensive care units between 2003 and 2008 were analyzed. The primary outcome was survival without major morbidity (defined as bronchopulmonary dysplasia, intraventricular hemorrhage grade 3 or 4, periventricular leukomalacia, retinopathy of prematurity stage 3, 4 or 5, or necrotizing enterocolitis stage 2 or 3). Trends in outcomes in relation to maternal age groups were examined using a multivariable analysis that controlled for confounders. RESULTS: Baseline comparison for the 12,326 eligible newborns revealed no differences in sex, small-for-gestational-age status, and chorioamnionitis among different maternal age groups. Higher rates of cesarean delivery, use of prenatal steroids, maternal hypertension, and diabetes were noted as maternal age increased (P<.01). Increasing maternal age was associated with increased survival without major morbidity (adjusted odds ratio [OR] 1.047, 95% confidence interval [CI] 1.001-1.095) and reductions in mortality (adjusted OR 0.922, 95% CI 0.855-0.955), necrotizing enterocolitis (adjusted OR 0.888, 95% CI 0.816-0.967), and sepsis (adjusted OR 0.904, 95% CI 0.862-0.948). CONCLUSION: Among preterm newborns, the odds of survival without major morbidity improved by 5% and mortality (8%), necrotizing enterocolitis (11%), and sepsis (9%) reduced as maternal age group increased by 5 years. LEVEL OF EVIDENCE: II.

Fetal tracheal occlusion in lambs with congenital diaphragmatic hernia: role of exogenous surfactant at birth.

Fetal tracheal occlusion (TO) has been used to reverse the lung hypoplasia associated with congenital diaphragmatic hernia (CDH). However, TO has a detrimental effect on type II pneumocyte function and surfactant production. Previously, we have shown that in surgically created CDH lambs, TO improved markedly the response to resuscitation even though the lungs remain surfactant deficient. The goal of this investigation was to assess the effects of exogenous surfactant administered at birth to CDH lambs with or without fetal TO during 8 h of resuscitation. Lambs were divided into five groups: CDH, CDH+surfactant (SURF), CDH+TO, CDH+TO+SURF, and nonoperated controls. A left-sided CDH was created in fetal lambs at 80 d gestation. TO was performed at 108 d, and the lambs were delivered by hysterotomy at 136 d. Bovine lipid extract surfactant was administered before the first breath and again at 4 h of life. All CDH+SURF lambs, but only three of five CDH lambs, survived up to 8 h. When compared with the corresponding nonsurfactant-treated group, surfactant-treated CDH and CDH+TO lambs did not demonstrate improved alveolar-arterial oxygen gradients, pH, or Pco(2). In fact, in the CDH+TO group, surfactant treatment significantly worsened ventilation efficiency as measured by the ventilation efficiency index. The observed improvement in pulmonary compliance secondary to surfactant treatment was not significant. This investigation demonstrates that prophylactic surfactant treatment at birth does not improve gas exchange or ventilation efficiency in CDH lambs with or without TO.

Lung function in lambs with diaphragmatic hernia after reversible fetal tracheal occlusion.

BACKGROUND/PURPOSE: Short-duration resuscitation (< or =4 hours) of lambs with diaphragmatic hernia treated in utero with tracheal occlusion have shown improved lung function compared with untreated diaphragmatic hernia. This may be a transient phenomenon in the treated diaphragmatic hernia lambs because of surfactant deficiency. Our objective was to analyze the effect of fetal tracheal occlusion with or without release of the occlusion 1 week before delivery on pulmonary function during a longer period of resuscitation (8 hours) in the diaphragmatic hernia lamb model. METHODS: Four groups were compared: diaphragmatic hernia (n = 5), diaphragmatic hernia and tracheal occlusion until delivery (n = 5), diaphragmatic hernia and tracheal occlusion with release of the occlusion 1 week before delivery (n = 5), and normal controls (n = 4). RESULTS: Despite persistently decreased surfactant levels, diaphragmatic hernia lambs treated with tracheal occlusion had normal-sized lungs with marked improvement in lung function and gas exchange over 8 hours when compared with untreated lambs with diaphragmatic hernia. Release of the tracheal occlusion 1 week before delivery added no benefit. CONCLUSIONS: It appears that surfactant-independent mechanisms such as pulmonary growth and structural changes are of foremost importance in relating to improved compliance, oxygenation, and ventilation of diaphragmatic hernia lambs treated with tracheal occlusion.