Oligohydramnios increases the risk of respiratory hospitalization in childhood: a population-based study

Interstitial lung disease in the newborn

Although relatively rare, interstitial lung diseases may present with respiratory distress in the newborn period. Most commonly these include developmental and growth disorders, disorders of surfactant synthesis and homeostasis, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy. Although the diagnosis of these disorders is sometimes made based on clinical presentation and imaging, due to the significant overlap between disorders and phenotypic variability, lung biopsy or, increasingly genetic testing is needed for diagnosis. These diseases may result in significant morbidity and mortality. Effective medical treatment options are in some cases limited and/or invasive. The genetic basis for some of these disorders has been identified, and with increased utilization of exome and whole genome sequencing even before lung biopsy, further insights into their genetic etiologies should become available.

Amniotic fluid content in children with kidney and urinary tract anomalies determines pre- and postnatal development

BACKGROUND

Renal oligohydramnios (ROH) describes an abnormally low volume of amniotic fluid (AF) during pregnancy. ROH is mostly caused by congenital fetal kidney anomalies. The ROH diagnosis frequently implies an increased risk of peri- and postnatal fetal mortality and morbidity. The present study aimed to evaluate the impact of ROH on pre-and postnatal development in children with congenital kidney anomalies.

METHODS

This retrospective study included 168 fetuses with anomalies in the kidney and urinary tract. Based on the amount of AF measured by ultrasound, patients were divided into three groups: normal amniotic fluid (NAF), amniotic fluid in the lower normal range (LAF), and ROH. These groups were compared with respect to prenatal sonographic parameters, perinatal outcomes, and postnatal outcomes.

RESULTS

Among the 168 patients with congenital kidney anomalies, 26 (15%) had ROH, 132 (79%) had NAF, and 10 (6%) had LAF. Of the 26 families affected by ROH, 14 (54%) decided to terminate pregnancy. Of 10 live-born children in the ROH group, 6 (60%) survived the observation time; of these, 5/6 presented with chronic kidney disease, stages I-III, at their last examination. The main differences in postnatal development between the ROH group and the NAF and LAF groups were: restricted height and weight gain, respiratory issues, complicated feeding, and the presence of extrarenal malformations.

CONCLUSIONS

ROH is not a mandatory indicator of severe postnatal kidney function impairment. However, children with ROH have complicated peri-and postnatal periods, due to the presence of concomitant malformations, which must be considered in prenatal care. A higher resolution version of the Graphical abstract is available as Supplementary information.

Assessment of the fetal lungs in utero

Antenatal diagnosis of abnormal pulmonary development has improved significantly over recent years because of progress in imaging techniques. Two-dimensional ultrasound is the mainstay of investigation of pulmonary pathology during pregnancy, providing good prognostication in conditions such as congenital diaphragmatic hernia; however, it is less validated in other high-risk groups such as those with congenital pulmonary airway malformation or preterm premature rupture of membranes. Three-dimensional assessment of lung volume and size is now possible using ultrasound or magnetic resonance imaging; however, the use of these techniques is still limited because of unpredictable fetal motion, and such tools have also been inadequately validated in high-risk populations other than those with congenital diaphragmatic hernia. The advent of advanced, functional magnetic resonance imaging techniques such as diffusion and T2* imaging, and the development of postprocessing pipelines that facilitate motion correction, have enabled not only more accurate evaluation of pulmonary size, but also assessment of tissue microstructure and perfusion. In the future, fetal magnetic resonance imaging may have an increasing role in the prognostication of pulmonary abnormalities and in monitoring current and future antenatal therapies to enhance lung development. This review aims to examine the current imaging methods available for assessment of antenatal lung development and to outline possible future directions.

Amniotic fluid volume at presentation with early preterm prelabor rupture of membranes and association with severe neonatal respiratory morbidity

OBJECTIVE

Amniotic fluid volume (AFV) plays an important role in early fetal lung development, and oligohydramnios in early pregnancy is associated with pulmonary hypoplasia. The aim of this study was to evaluate the association between AFV at the time of presentation with early preterm prelabor rupture of membranes (PPROM) and severe neonatal respiratory morbidity and other adverse pregnancy outcomes.

METHODS

This was a retrospective study of all women with a singleton pregnancy, admitted to a single tertiary referral center between 2004 and 2014, for expectant management of PPROM at 20 + 0 to 28 + 6 weeks' gestation. The primary exposure was AFV at presentation, classified according to sonographic maximum vertical pocket (MVP) as: normal AFV (> 2 cm), oligohydramnios (≤ 2 cm and > 1 cm) or severe oligohydramnios (≤ 1 cm). The primary outcome was a composite variable of severe respiratory morbidity, defined as either of the following: (1) need for respiratory support in the form of mechanical ventilation using an endotracheal tube for ≥ 72 h and need for surfactant; or (2) bronchopulmonary dysplasia, defined as requirement for oxygen at postmenstrual age of 36 weeks or at the time of transfer to a Level-II facility. Adjusted odds ratios (aOR) and 95% CI for the primary and secondary outcomes were calculated for each AFV-at-presentation group (using normal AFV as the reference), adjusting for gestational age (GA) at PPROM, latency period, birth weight, mode of delivery and chorioamnionitis.

RESULTS

In total, 580 women were included, of whom 304 (52.4%) had normal AFV, 161 (27.8%) had oligohydramnios and 115 (19.8%) had severe oligohydramnios at presentation. The rates of severe respiratory morbidity were 16.1%, 26.7% and 45.2%, respectively. Compared with normal AFV at presentation, oligohydramnios (aOR, 3.27; 95% CI, 1.84-5.84) and severe oligohydramnios (aOR, 4.11; 95% CI, 2.26-7.56) at presentation were associated independently with severe respiratory morbidity. Other variables that were associated independently with the primary outcome were GA at PPROM (aOR, 0.54; 95% CI, 0.43-0.69), latency period (aOR, 0.94; 95% CI, 0.91-0.98) and Cesarean delivery (aOR, 2.01; 95% CI, 1.21-3.32).

CONCLUSIONS

In women with early PPROM, AFV at presentation, as assessed by the MVP on ultrasound examination, is associated independently with severe neonatal respiratory morbidity. This information may be taken into consideration when counseling women with early PPROM regarding neonatal outcome and management options. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Isolated oligohydramnios and long-term neurological morbidity of the offspring

This study aimed to assess the association between maternal-isolated oligohydramnios (IO) and offspring long-term neurological complications. A population-based retrospective cohort study was conducted, including all births at a single tertiary medical center in Israel between the years 1991 and 2014. Multiple pregnancies and potential pregnancy complications associated with oligohydramnios were excluded. The computerized obstetrical database was linked with the computerized dataset of all pediatric hospitalizations of the same medical center. Evaluation of cumulative neurological-associated hospitalizations rate over time was compared using a Kaplan-Meier survival curve. The Weibull survival parametric model was conducted to assess the neurological-associated hospitalization risk in the presence of IO, while accounting for potential confounders. A total of 190,259 pregnancies were included in the study, of which 4063 (2.13%) pregnancies were complicated with IO. Total neurological-related hospitalizations were significantly more common in the IO group (3.7% in the IO group and 3.0% in the comparison group, p = 0.005). Pervasive developmental disorder, movement disorders, developmental disorders, and degenerative and demyelization disorders were all specific neurological diagnoses significantly more common in the exposed group. The survival curve demonstrated a significantly higher cumulative hospitalization rate in the exposed group (log-rank p = 0.001). Using a multivariate model adjusting for gestational age, maternal age, and labor induction, an independent association between IO and long-term neurological morbidity of the offspring was observed (adjusted hazard ratio 1.203; 95% CI 1.02-1.42). In summary, a significant association was found between pregnancies complicated by IO and long-term neurological morbidity of the offspring.

Pulmonary Hypoplasia Induced by Oligohydramnios: Findings from Animal Models and a Population-Based Study

Pulmonary hypoplasia is a substantial cause of death in newborn infants, and oligohydramnios is one of the most commonly associated abnormalities. Lung growth is influenced by physical factors such as the intrauterine space, lung liquid volume and pressure, and fetal breathing movements. During lung development, the main physical force experienced by the lungs is stretching induced by breathing movements and the lung fluid in the airspaces. Oligohydramnios reduces the intrathoracic cavity size, thus disrupting fetal lung growth and leading to pulmonary hypoplasia. The exact mechanism by which oligohydramnios alters the respiratory system structure and the effect of oligohydramnios on long-term respiratory outcomes remain unknown. In this review, we summarize the effects of oligohydramnios on lung development, discuss the mechanisms of oligohydramnios-induced pulmonary hypoplasia identified in various animal studies, and describe the long-term respiratory outcomes in childhood of oligohydramnios-exposed fetuses reported by a population-based study.

Development of the lung

To fulfill the task of gas exchange, the lung possesses a huge inner surface and a tree-like system of conducting airways ventilating the gas exchange area. During lung development, the conducting airways are formed first, followed by the formation and enlargement of the gas exchange area. The latter (alveolarization) continues until young adulthood. During organogenesis, the left and right lungs have their own anlage, an outpouching of the foregut. Each lung bud starts a repetitive process of outgrowth and branching (branching morphogenesis) that forms all of the future airways mainly during the pseudoglandular stage. During the canalicular stage, the differentiation of the epithelia becomes visible and the bronchioalveolar duct junction is formed. The location of this junction stays constant throughout life. Towards the end of the canalicular stage, the first gas exchange may take place and survival of prematurely born babies becomes possible. Ninety percent of the gas exchange surface area will be formed by alveolarization, a process where existing airspaces are subdivided by the formation of new walls (septa). This process requires a double-layered capillary network at the basis of the newly forming septum. However, in parallel to alveolarization, the double-layered capillary network of the immature septa fuses to a single-layered network resulting in an optimized setup for gas exchange. Alveolarization still continues, because, at sites where new septa are lifting off preexisting mature septa, the required second capillary layer will be formed instantly by angiogenesis. The latter confirms a lifelong ability of alveolarization, which is important for any kind of lung regeneration.