Pregnancy outcome of fetuses with trisomy 18 identified by prenatal sonography and chromosomal analysis in a perinatal center

To investigate the pregnancy outcome of fetuses affected with trisomy 18, we analyzed 63 cases diagnosed at our hospital from January 1993 to December 2004. Twenty-nine were males and 34 were females. Fifty-eight were prenatally diagnosed, and in 16 (27.6%) of them intrauterine fetal death (IUFD) occurred between 28 weeks and 41 weeks gestation (34.6 +/- 3.9 weeks, Mean +/- SD). Ten (17.2%) fetuses died during labor and their age ranged from 30 weeks to 40 weeks of gestation. The total number of cases ending in fetal demise was 26 (44.8%) and the mean gestational age at the time of fetal demise was 35.0 +/- 3.6 weeks (Mean +/- SD). All liveborn infants (n = 36) were born after 31 weeks gestation. In our study the preterm birth ratio for trisomy 18 is 34.8%, which is much higher than the ratio for the general population. Females are more likely than males to be long-term survivors. These data are helpful in the counseling of parents faced with the difficult decision of whether or not to continue a pregnancy with a fetus affected with trisomy 18.