first trimester, from 10 to 13 weeks of gestation, has now emerged as an important indication for fetal echocardiography Indeed, increased nuchal translucency of greater than 3 mm as seen during scanning when the fetus is from 10 to 14 weeks of age is a published marker for aneuploidy.18–23 Even in the absence of a chromosomal anomaly, fetuses found to have increased nuchal translucency on early scanning have been shown to be at increased risk for congenital cardiac disease.24–26 Fetuses conceived via artificial fertilization, particularly when intracytoplasmic injection of sperm is used, have a twofold increased risk of major birth defects, including congenital cardiac disease, compared with infants conceived naturally.27 Therefore fetal echocardiography has emerged as a benefit to this group of patients Box 8.1 Indications for Fetal Echocardiography Maternal Indications ■ Family history of congenital cardiac disease ■ Metabolic disorders, such as phenylketonuria or diabetes ■ Exposure to teratogens ■ Exposure to inhibitors of prostaglandin synthetase, such as ibuprofen, salicylic acid, or indomethacin ■ Infection with rubella ■ Autoimmune disease, such as systemic lupus erythematosus, or Sjögren syndrome ■ Familial inherited disorders, such as Ellis van Creveld syndrome, Marfan syndrome, or Noonan syndrome ■ Artificial fertilization Fetal Indications ■ Abnormal result following obstetric ultrasonic screening ■ Extracardiac abnormality ■ Chromosomal abnormality ■ Arrhythmia ■ Hydrops ■ Increased nuchal translucency in first trimester ■ Multiple gestation and twin-twin transfusion Timing of Fetal Echocardiography Fetal echocardiography is best performed between 18 and 22 weeks’ gestation At this gestational age there is adequate amniotic fluid to allow good visualization of the cardiac structures and vasculature After 30 weeks’ gestation, increase in the fetal body mass and the shadowing effects of the fetal ribs may make the acquisition of images more difficult Maternal transabdominal fetal imaging may be performed between 15 and 18 weeks’ gestation, although visualization may be suboptimal At some centers, first-trimester screening for congenital heart disease may occur as early as 10 to 14 weeks’ gestation, especially in populations known to be at high risk, such as those noted to have increased nuchal translucency during scanning at 10 to 14 weeks, those with suspected aneuploidy, or those with a family history of congenital cardiac disease.28 Feasibility studies have demonstrated adequate image acquisition at these gestational ages for both maternal transabdominal and transvaginal imaging.28–30 At some centers with experienced practitioners, the prenatal detection rate for major congenital heart disease exceeds 86% to 90% within the first trimester.29,30