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. 2006 Wiley Periodicals, Inc.