Transferring an extremely premature infant to an extra-uterine life support system: a prospective view on the obstetric procedure

To improve care for extremely premature infants, the development of an extrauterine environment for newborn development is being researched, known as Artificial Placenta and Artificial Womb (APAW) technology. APAW facilitates extended development in a liquid-filled incubator with oxygen and nutrient supply through an oxygenator connected to the umbilical vessels. This setup is intended to provide the optimal environment for further development, allowing further lung maturation by delaying gas exposure to oxygen. This innovative treatment necessitates interventions in obstetric procedures to transfer an infant from the native to an artificial womb, while preventing fetal-to-neonatal transition. In this narrative review we analyze relevant fetal physiology literature, provide an overview of insights from APAW studies, and identify considerations for the obstetric procedure from the native uterus to an APAW system. Lastly, this review provides suggestions to improve sterility, fetal and maternal well-being, and the prevention of neonatal transition.

Cardiorespiratory consequences of intrauterine growth restriction: Influence of timing, severity and duration of hypoxaemia

At birth, weight of the neonate is used as a marker of the 9-month journey as a fetus. Those neonates born less than the 10th centile for their gestational age are at risk of being intrauterine growth restricted. However, this depends on their genetic potential for growth and the intrauterine environment in which they grew. Alterations in the supply of oxygen and nutrients to the fetus will decrease fetal growth, but these alterations occur due to a range of causes that are maternal, placental or fetal in nature. Consequently, IUGR neonates are a heterogeneous population. For this reason, it is likely that these neonates will respond differently to interventions compared not only to normally grown fetuses, but also to other neonates that are IUGR but have travelled a different path to get there. Thus, a range of models of IUGR should be studied to determine the effects of IUGR on the development and function of the heart and lung and subsequently the impact of interventions to improve development of these organs. Here we focus on a range of models of IUGR caused by manipulation of the maternal, placental or fetal environment on cardiorespiratory outcomes.

Improvement of cardiac function in fetuses with growth restriction following antenatal betamethasone administration: fact or artifact?

INTRODUCTION

Use of corticosteroids for fetal lung maturation has reduced the perinatal mortality/morbidity from prematurity related complications. There is a paucity of studies evaluating the effect of steroid administration on the fetal circulation and cardiac function in fetal growth restriction (FGR). The aim of the study was to assess changes in fetal Doppler indices and cardiovascular function in pregnancies complicated with FGR after administration of betamethasone.

METHODS

This was a prospective study conducted in a tertiary care research center between July 2017 and May 2018. Pregnant women with FGR between 28 and 36 weeks' gestation, who were scheduled to receive betamethasone (two doses of 12 mg, 24 h apart) were recruited. Fetal cardiovascular function in fetuses FGR was assessed immediately before first dose and once between 6 and 24 h after the second dose of betamethasone by the same operator. Wilcoxon matched-pairs signed-rank test or paired t-tests were used to compare parameters before and after corticosteroid exposure.

RESULTS

Fifty cases with FGR were evaluated before and after administration of betamethasone, at mean gestational age of 34.6 ± 2.0 weeks. Fetal heart rate (148.78 ± 9.10 versus 144.73 ± 9.61, p < .001), left heart myocardial performance index ([MPI], 0.66 ± 0.06 versus 0.55 ± 0.09, p ≤ .001) and right heart MPI (0.65 ± 0.04 versus 0.63 ± 0.04, p .016) showed improvement after steroids. Left heart isovolumic relaxation and contraction indices along with ejection time of both sides showed a small but statistically significant improvement (p < .001), but other fetal cardiac functional and Doppler indices remain unchanged after steroids.

CONCLUSIONS

Fetal heart rate, cardiac MPI, left sided isovolumic indices showed an improvement after betamethasone administration. Follow up studies are needed to ascertain whether these effects persist in the long term and to determine whether these are beneficial to a growth restricted fetuses.

Chronic hypoxaemia as a molecular regulator of fetal lung development: implications for risk of respiratory complications at birth

Exposure to altered intrauterine conditions during pregnancy influences both fetal growth and organ development. Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction (IUGR) that may influence the risk of infants experiencing respiratory complications at birth. There are a variety of signalling pathways that contribute to normal fetal lung development at the molecular level. The specific molecular effects of chronic hypoxaemia associated with IUGR on lung development are likely to be dependent on the specific aetiology (maternal, placental and/or fetal factors) that can alter hormone concentrations, oxygen and nutrient transport to the fetus. This review discusses molecular pathways that may contribute to altered fetal lung maturation following exposure to chronic hypoxaemia. Importantly, these studies highlight that the heterogeneity in respiratory outcomes at birth in this obstetric subpopulation are likely determined by the timing, severity and duration of chronic hypoxaemia encountered by the fetus during pregnancy.

Effect of corticosteroids on cardiac function in growth-restricted fetuses

OBJECTIVE

To determine the acute effects of corticosteroids on the cardiovascular system in growth-restricted fetuses.

METHODS

This was a prospective cohort study conducted at a tertiary hospital between January 2011 and October 2013. Fetal cardiovascular function in fetuses with intrauterine growth restriction (IUGR) was assessed immediately before and 24 h after the first dose of betamethasone, administered in routine management of IUGR. Fetal arterial and venous Dopplers were assessed. Fetal cardiac function was evaluated by tissue Doppler echocardiography, with the assessment of both left and right ventricular function by calculating myocardial performance index (MPI') and E':A' ratios. Values were compared before and after exposure.

RESULTS

Seventeen patients were included at a mean gestational age of 34 + 1 (range, 29 + 1 to 37 + 4) weeks. Fifteen fetuses were below the 5(th) percentile and two were below the 10(th) percentile for estimated fetal weight and abdominal circumference and all had no interval growth during a 2-week period. There was a decrease in right MPI' (from 0.56 to 0.47; P = 0.007) after corticosteroid exposure but no change in left MPI' (from 0.49 to 0.48). Right MPI' was higher than left MPI' before exposure (0.56 vs 0.49, respectively; P = 0.001), but not after exposure (P = 0.55). There was no change in left or right ventricular E':A' ratios and no difference was detected in umbilical artery, middle cerebral artery or ductus venosus pulsatility index following administration of corticosteroids.

CONCLUSIONS

Corticosteroids altered right-sided, but not left-sided, tissue Doppler MPI' in IUGR fetuses, with no detectable change in arterial or venous Doppler pulsatility indices. Before exposure, the mean right MPI' was higher than the left. However, after exposure, there was no difference, suggesting that corticosteroids may reverse the negative effect of IUGR on fetal heart function. Large prospective studies with a larger sample size are needed to confirm this finding. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Association of Antenatal Corticosteroids With Mortality, Morbidity, and Neurodevelopmental Outcomes in Extremely Preterm Multiple Gestation Infants

IMPORTANCE

Little is known about the effects of antenatal corticosteroids (ANS) on extremely preterm multiples.

OBJECTIVE

To examine if use of ANS is associated with improvement in major outcomes in extremely preterm multiples.

DESIGN, SETTING, AND PARTICIPANTS

Infants with a gestational age between 22 and 28 weeks born at a National Institute of Child Health and Human Development Neonatal Research Network center were studied between January 1998 and December 2013. Generalized estimating equation models were used to generate adjusted relative risks (aRR) controlling for important maternal and neonatal variables.

EXPOSURE

Antenatal corticosteroids.

MAIN OUTCOMES AND MEASURES

In-hospital mortality and the composite outcome of neurodevelopmental impairment at 18 to 22 months' corrected age or death before assessment.

RESULTS

A total of 6925 multiple-birth infants were studied; 5775 of 6925 (83.4%) were twins, and 4276 (61.7%) were white. Of the total study population, 6094 (88%) were born to women who received ANS. In-hospital mortality was lower among infants with exposure to ANS vs no exposure (aRR = 0.87; 95% CI, 0.78-0.96). Neurodevelopmental impairment or death was not significantly lower among those exposed to ANS vs no exposure (aRR = 0.93; 95% CI, 0.84-1.03). Other adverse outcomes that occurred less frequently among infants of women receiving ANS included severe intraventricular hemorrhage (aRR = 0.68; 95% CI, 0.58-0.78) and the combined outcomes of necrotizing enterocolitis or death and severe intraventricular hemorrhage or death. Subgroup analyses indicated that exposure to ANS was associated with a lower risk of mortality and a lower composite of neurodevelopmental impairment or mortality among nonsmall for gestational age multiples (aRR = 0.82; 95% CI, 0.74-0.92; and aRR = 0.89; 95% CI, 0.80-0.98, respectively) and a higher risk among small for gestational age multiples (aRR = 1.40; 95% CI, 1.02-1.93; and aRR = 1.62; 95% CI, 1.22-2.16, respectively). Antenatal corticosteroids were associated with higher neurodevelopmental impairment or mortality among multiple-birth infants of mothers with diabetes (aRR = 1.55; 95% CI, 1.00-2.38) but not among infants of mothers without diabetes (aRR = 0.91; 95% CI, 0.83-1.01).

CONCLUSIONS AND RELEVANCE

Compared with no exposure, exposure to ANS was associated with a lower risk of mortality in extremely preterm multiples, with no significant differences in the composite of neurodevelopmental impairment or death. Future research should investigate the increased risks of mortality and the composite of neurodevelopmental impairment or death associated with exposure to corticosteroids among small for gestational age multiples.

Evolution, Development, and Function of the Pulmonary Surfactant System in Normal and Perturbed Environments

Surfactant lipids and proteins form a surface active film at the air-liquid interface of internal gas exchange organs, including swim bladders and lungs. The system is uniquely positioned to meet both the physical challenges associated with a dynamically changing internal air-liquid interface, and the environmental challenges associated with the foreign pathogens and particles to which the internal surface is exposed. Lungs range from simple, transparent, bag-like units to complex, multilobed, compartmentalized structures. Despite this anatomical variability, the surfactant system is remarkably conserved. Here, we discuss the evolutionary origin of the surfactant system, which likely predates lungs. We describe the evolution of surfactant structure and function in invertebrates and vertebrates. We focus on changes in lipid and protein composition and surfactant function from its antiadhesive and innate immune to its alveolar stability and structural integrity functions. We discuss the biochemical, hormonal, autonomic, and mechanical factors that regulate normal surfactant secretion in mature animals. We present an analysis of the ontogeny of surfactant development among the vertebrates and the contribution of different regulatory mechanisms that control this development. We also discuss environmental (oxygen), hormonal and biochemical (glucocorticoids and glucose) and pollutant (maternal smoking, alcohol, and common "recreational" drugs) effects that impact surfactant development. On the adult surfactant system, we focus on environmental variables including temperature, pressure, and hypoxia that have shaped its evolution and we discuss the resultant biochemical, biophysical, and cellular adaptations. Finally, we discuss the effect of major modern gaseous and particulate pollutants on the lung and surfactant system.

The Effects of Antenatal Corticosteroids on Short- and Long-Term Outcomes in Small-for-Gestational-Age Infants

AIM

To evaluate the effect of antenatal corticosteroids (ANS) on short- and long-term outcomes in small-for-gestational age (SGA) infants.

METHODS

A retrospective database analysis was performed. A total of 1,931 single infants (birth weight <1,500 g) born at a gestational age between 22 weeks and 33 weeks 6 days who were determined to be SGA registered in the Neonatal Research Network Database in Japan between 2003 and 2007 were evaluated for short-term outcome and long-term outcome.

RESULTS

ANS was administered to a total of 719 infants (37%) in the short-term outcome evaluation group and 344 infants (36%) in the long-term outcome evaluation group. There were no significant differences between the ANS group and the no-ANS group for primary short-term outcome (adjusted odds ratio (OR) 0.73; 95% confidence interval (CI) 0.45-1.20; P-value 0.22) or primary long-term outcome (adjusted OR 0.69; 95% CI 0.40-1.17; P-value 0.17).

CONCLUSIONS

Our results show that ANS does not affect short- or long-term outcome in SGA infants when the birth weight is less than 1500 g. This study strongly suggests that administration of ANS resulted in few benefits for preterm FGR fetuses.

Antenatal steroids and the IUGR fetus: are exposure and physiological effects on the lung and cardiovascular system the same as in normally grown fetuses?

Glucocorticoids are administered to pregnant women at risk of preterm labour to promote fetal lung surfactant maturation. Intrauterine growth restriction (IUGR) is associated with an increased risk of preterm labour. Hence, IUGR babies may be exposed to antenatal glucocorticoids. The ability of the placenta or blood brain barrier to remove glucocorticoids from the fetal compartment or the brain is compromised in the IUGR fetus, which may have implications for lung, brain, and heart development. There is conflicting evidence on the effect of exogenous glucocorticoids on surfactant protein expression in different animal models of IUGR. Furthermore, the IUGR fetus undergoes significant cardiovascular adaptations, including altered blood pressure regulation, which is in conflict with glucocorticoid-induced alterations in blood pressure and flow. Hence, antenatal glucocorticoid therapy in the IUGR fetus may compromise regulation of cardiovascular development. The role of cortisol in cardiomyocyte development is not clear with conflicting evidence in different species and models of IUGR. Further studies are required to study the effects of antenatal glucocorticoids on lung, brain, and heart development in the IUGR fetus. Of specific interest are the aetiology of IUGR and the resultant degree, duration, and severity of hypoxemia.

Long term respiratory consequences of intrauterine growth restriction

Epidemiological studies demonstrate that in-utero growth restriction and low birth weight are associated with impaired lung function and increased respiratory morbidity from infancy, throughout childhood and into adulthood. Chronic restriction of nutrients and/or oxygen during late pregnancy causes abnormalities in the airways and lungs of offspring, including smaller numbers of enlarged alveoli with thicker septal walls and basement membranes. The structural abnormalities and impaired lung function seen soon after birth persist or even progress with age. These changes are likely to cause lung symptomology through life and hasten lung aging.

Intrauterine growth restriction delays surfactant protein maturation in the sheep fetus

Pulmonary surfactant is synthesized by type II alveolar epithelial cells to regulate the surface tension at the air-liquid interface of the air-breathing lung. Developmental maturation of the surfactant system is controlled by many factors including oxygen, glucose, catecholamines, and cortisol. The intrauterine growth-restricted (IUGR) fetus is hypoxemic and hypoglycemic, with elevated plasma catecholamine and cortisol concentrations. The impact of IUGR on surfactant maturation is unclear. Here we investigate the expression of surfactant protein (SP) A, B, and C in lung tissue of fetal sheep at 133 and 141 days of gestation (term 150 +/- 3 days) from control and carunclectomized Merino ewes. Placentally restricted (PR) fetuses had a body weight <2 SD from the mean of control fetuses and a mean gestational Pa(O(2)) <17 mmHg. PR fetuses had reduced absolute, but not relative, lung weight, decreased plasma glucose concentration, and increased plasma cortisol concentration. Lung SP-A, -B, and -C protein and mRNA expression was reduced in PR compared with control fetuses at both ages. SP-B and -C but not SP-A mRNA expression and SP-A but not SP-B or -C protein expression increased with gestational age. Mean gestational Pa(O(2)) was positively correlated with SP-A, -B, and -C protein and SP-B and -C mRNA expression in the younger cohort. SP-A and -B gene expression was inversely related to plasma cortisol concentration. Placental restriction, leading to chronic hypoxemia and hypercortisolemia in the carunclectomy model, results in significant inhibition of surfactant maturation. These data suggest that IUGR fetuses are at significant risk of lung complications, especially if born prematurely.