Cardiac anatomy screening: what is the best time for screening in pregnancy?

To consider the ideal gestational age for cardiac evaluation during pregnancy.

Screening the heart during routine obstetric ultrasound has become well established and is increasingly successful in the initial detection of major congenital heart disease. When the option of termination of pregnancy is available, the earlier the diagnosis of any major fetal malformation is made, the better for the patient. An important group who have recently been found to be at increased risk of fetal heart malformation are those with increased nuchal translucency measurements, who are identified between 11 and 14 weeks. Thus, screening for fetal anomalies is being attempted much earlier in pregnancy, aided by advances in technology. However, some forms of cardiac malformations do not become evident until the third trimester of pregnancy; as a result, some of the late-developing lesions may go undetected during very early evaluation.

The ideal timing for screening is a compromise between obtaining adequate images for diagnosis in the majority of routine patients, scanning sufficiently late not to miss late-developing lesions and yet offering diagnosis as early as possible for parents to consider their options, if there are any applicable to their particular diagnosis. For low-risk patients, the best compromise appears to be at around 20 weeks of gestation. For patients at increased risk of congenital heart disease, such as those found to have substantially increased nuchal translucency or those with a family history of the disease, an initial scan to exclude major malformations should be performed by the fetal cardiology expert at 12-14 weeks, with follow-up at around 20 weeks to exclude more minor defects and those lesions which may become evident later.