Congenital heart defects were almost three times as likely to complicate the monochorionic/diamniotic twin gestations affected by twin-to-twin transfusion syndrome (TTTS), compared with those without TTTS, but an increase occurred regardless of the presence of TTTS. Ventricular septal defects were among the most frequent heart defects. Fetal echocardiography may be considered for all monochorionic/diamniotic twin gestations.
Dr. Copel disclosed that he has received research support from Philips Healthcare and Siemens Healthcare. Both companies manufacture echocardiography and other ultrasound systems.
A two-dimensional four-chamber view of a normal fetal heart (left). Fetal image of a complete atrioventricular septal defect with large atrial (**) and ventricular (*) septal defects (right).
Source Images: © Elsevier Inc.
Diagnosing Birth Defects
Birth defects continue to account for the majority of infant deaths, and their biologic basis continues to present a mixed picture, with the majority of causes still unknown. Cardiac defects – the most common type of birth defect – result in varying types of morbidity, but remain the most severe and disabling of all birth defects. As our guest author points out below, cardiovascular defects are the single largest contributor to birth defect–attributable infant mortality.
What is clear is the fact that when birth defects are identified prenatally, decisions can be made regarding the timing and route of delivery and even the facility where delivery occurs. We know that such decision making can be highly influential on the ultimate outcome of the infant.
Fortunately, there has been improvement in recent years in diagnostic technology that enables more prenatal diagnosis of congenital heart disease, and certain conditions that in the past went unknown or undiagnosed are now being identified early so that specialists can intervene in a timely manner.
While certain pregnancies are clearly at higher risk – those involving mothers who have pregestational diabetes, for instance, or mothers with exposure to particular toxins – there are other scenarios and factors that increase risk of which we should be aware.
It's a tricky evaluative process, for, as our guest author points out, most infants born with congenital heart disease do not have defined risk factors. At the least, however, we can be aware of the familial, maternal, and fetal factors that are known to increase risk and then ensure that all at-risk pregnancies are properly evaluated – often with fetal echocardiography – to determine if a cardiac defect is present and, if so, to plan the delivery-related issues of timing, mode, and facility.
In light of the importance of this subject and the role that ultrasound scanning, genetic counseling, and early decision making and planning can play in the ultimate outcome of the fetus, we decided to do a Master Class on congenital heart defects. We have invited Dr. Joshua A. Copel, professor of obstetrics, gynecology, and reproductive services, and of pediatrics, and vice chair of obstetrics at Yale University, New Haven, Conn., to serve as our guest professor.
Dr. Copel has written and lectured extensively on fetal arrhythmias, fetal cardiac anomalies and congenital heart disease, and sonographic monitoring and fetal echocardiography. Here he discusses what we should know about both familial contributions to congenital heart disease and various noninherited risk factors.