Effect of Lung Expansion on the Fetal Lamb Circulation

The change in pulmonary blood flow as a result of expansion of the lungs with 100-200 ml of nitrogen was studied in eleven fetal lambs. The fetal circulation was evaluated by simultaneous injection of 5% sodium chloride into the left ventricle and indocyanine green into the right ventricle and by recording the concentration of these indicators in the right carotid artery and right femoral artery. During the control period, prior to lung expansion, most of the right ventricular output bypassed the lungs; in fact, there was no detectable pulmonary blood flow in six of the lambs. As long as the lungs were forcibly maintained expanded there was no increase in pulmonary blood flow, but when the expanding nitrogen was given free outlet again there was a change in the distribution of right ventricular output in nine of the lambs. The portion passing through the lungs increased in eight lambs but decreased in one. In two lambs the lungs were expanded with 100 ml of Dextran. This did not affect pulmonary blood flow although the following expansion with 100 ml of nitrogen in both instances caused more of the right ventricular output to be distributed to the lungs. It is concluded that surface tension in the newly formed air-liquid interfaces of the expanded alveoli may decrease resistance to pulmonary blood flow.     

Agenesis of the Ductus Venosus and its Correlation to Hydrops Fetalis and the Fetal Hepatic Circulation: Case Reports and Review of the Literature

Under normal conditions about 50% of the placental venous return bypasses the liver through the ductus venosus. This blood flow is preferentially directed toward the foramen ovale and provides optimum oxygenation to the fetal heart and brain. Absence of the ductus venosus is a rare vascular anomaly, the significance of which has been disputed. We distinguish the pattern in which the liver is entirely bypassed, a manifestation of a fundamental malformation in the umbilical venous system, from the pattern in which the ductus venosus is absent despite a normal course of the umbilical vein. We review the literature regarding the latter and report eight new cases. Three of the four previously reported cases showed associated malformations and two of them suffered from portal congestion and hydrops. Among our eight cases three showed severe malformations in the cardiovascular system. Three cases presented themselves with hydrops fetalis and disturbance in the portal circulation, and two cases expressed signs of intrauterine asphyxia. The absence of the ductus venosus might be a minor vascular maldevelopment resulting in an early disturbance in the portal circulation. Our findings suggest that this anomaly might induce hydrops fetalis.     

Fetal cardiology

A systematic approach to examination of the fetal heart will enhance the detection of structural cardiac abnormalities and will enable an accurate diagnosis of congenital heart disease to be made. Once an abnormality has been detected appropriate counselling must be provided and adequate support given to the parents. Associated extracardiac abnormalities should be sought for, and plans for the remainder of pregnancy, delivery and postnatal management should be made using a team approach. In cases resulting in termination of pregnancy, permission for autopsy should be sought to confirm the ultrasound diagnosis. Although in-utero therapy is available for some forms of fetal arrhythmia and a few limited cases of structural heart disease, this should be conducted in tertiary centres.     

Fetal hydrothorax

Three cases of bilateral congenital hydrothorax concomitant with hydrops fetalis are presented and compared with similar cases in literature. The hydrops fetalis to our opinion is caused by peripheral hypoxia. The hypoxia has its origin in the restricted cardiac output caused by the bilateral hydrothorax.     

Fetal therapy

The advances in fetal therapy including endoscopic approaches and the advent of safer anesthetic techniques has led to the intrauterine management of potentially lethal diseases or diseases associated with high morbidity. This review will elicit certain newer techniques for fetal therapy including their application and complications.     

Fetal magnetoencephalography

The assessment of the neurological integrity of the human fetus in utero is a technically challenging problem. New brain imaging devices can substantially improve our capabilities to describe functional brain activity in the fetus. It has been well established by fetal behavioral studies and investigations in preterm and term newborns that the brain is functional in utero. The major effort required to perform effective neurological functional investigations is designation of an integrated approach to neurological assessment and the generation of normative data. Currently, it is possible to record evoked brain activity elicited by auditory and visual stimulation from the fetus. In addition, there is growing evidence that spontaneous brain activity can be recorded in the fetus. This paper explores the current status of the brain-imaging field for fetal investigations and currently available data.     

Fetal thrombocytopenia

Fetal thrombocytopenia is most often caused by maternal alloantibodies against fetal platelets crossing the placenta and resulting in platelet destruction. This condition, known as fetal and neonatal alloimmune thrombocytopenia, is usually detected after the birth of a symptomatic child who shows signs of bleeding in the skin or in the brain. In the most severe cases, intracranial hemorrhage leads to severe handicap or death. The challenge for the clinician is to provide preventive treatment in the next pregnancy. The current cornerstone of this treatment is maternal intravenous administration of immunoglobulins during the second half of pregnancy.     

Fetal cardiology

The prevalence of congenital heart disease increases with increasing NT, and many defects can be detected by echocardiography performed by a specialist at 13 to 17 weeks. There is increasing evidence that a prenatal diagnosis improves fetal outcome. Physiology and pathophysiology of the human fetal pulmonary circulation play an important role in the fetal circulation, and recent studies about the reactivity of these vessels in the third trimester have contributed to increase our understanding. The main issue in fetal arrhythmias (brady- and tachycardia) is the correct indication, efficacy, and safety of treatment.     

Fetal arrhythmias

Fetal arrhythmias may be benign or life-threatening. Benign disturbances in fetal cardiac rhythm are relatively common, and their clinical manifestations are reviewed. Life-threatening fetal arrhythmias include supraventricular tachycardias, atrial flutter, ventricular or junctional tachycardia, chaotic atrial tachycardia, and bradyarrhythmias such as second or third degree AV block. The incidence, diagnostic characteristics and treatment of each of these are reviewed. In addition, the pathophysiology of hydrops fetalis, embryology of the conduction system and transplacental drug transfer characteristics are reviewed.