Ectopia cordis in a fetus with trisomy 18.

Trisomy 18 is the second-most common autosomal trisomy and represents one third of the chromosomal trisomies identified prenatally. We present a case of a fetus with trisomy 18 in which thoracoabdominal ectopia cordis was detected prenatally; it was noted as a dominant defect on a sonographic examination performed at 19 weeks' gestation. Furthermore, our case exhibits a rare type of multiple-marker screening result with increased maternal serum alpha-fetoprotein. This case demonstrates the need for thorough sonographic evaluation of the fetal thoracoabdominal wall as early as possible, because fetal ectopia cordis can be the major abnormality of trisomy 18.