Diagnosis and Prevention of Abnormal Antenatal Lung Growth

Abnormal antenatal lung growth can result in a high mortality and morbidity, thus accurate diagnosis and effective preventative measures are essential. We have critically reviewed the literature to identify whether current diagnostic tools yield results predictive of outcome and whether antenatal interventions do prevent abnormal lung growth. Three-dimensional (3D) ultrasound examination provides more accurate information than 2D ultrasound on fetal lung volume prior to 34 weeks of gestation, but can be inaccurate if there is oligohydramnios. In addition, fetal lung volumes obtained by 3D ultrasound analysed by Virtual Organ Computer Aided analysis (VOCAL) can predict neonatal respiratory outcomes. Fetal lung volume assessments by magnetic resonance imaging (MRI) correlate with lung to head ratio results obtained by 2D ultrasound results, with an observed/expected ratio of 0.25 predicting poor survival. MRI using quantitative signal analysis gives a functional assessment of the lung parenchyma. MRI, however, is expensive and has limited patient acceptability. Antenatal interventions attempting to prevent pulmonary hypoplasia include amnioinfusion which can relieve oligohydramnios in preterm, premature rupture of the membranes, but there are insufficient data on longer term outcomes to recommend it for routine practice. In severe idiopathic oligohydramnios, amnio-infusion might prolong the duration of the pregnancy, but there is no evidence to date that it improves neonatal mortality. Thoracoamniotic shunting results in effective drainage of pleural effusions facilitating resuscitation, but it is usually performed too late in pregnancy to influence lung growth and there are complications. Pleural effusions can also be managed by pleurodesis using either OK-432 or autologous blood. In fetuses with a congenital diaphragmatic hernia (CDH) obstruction of the normal egress of fetal lung fluid by placing a balloon in the trachea (fetal tracheal obstruction (FETO)) in non randomized studies, appear to improve survival. The results of randomised trials of FETO with long term outcomes are eagerly awaited.