An Unusual Case: Testing for Fetal Trisomy Abnormalities in Maternal Blood at 33-Week Gestation


Poster Presentation


In 1997, the detection of fetal deoxyribonucleic acid (DNA) in maternal circulation suggested the future of noninvasive prenatal testing. It is estimated that 95% of all women opt for prenatal screening. Reasons may include the desire to prepare for the birth of an affected child; preparation for the possibility of an in utero or neonatal death; planning for the time, mode, and place of delivery; planning for specialists to care for the affected child; and options for termination. Invasive tests carry a risk of injury to the fetus and are not 100% accurate. Fetal DNA testing for aneuploidy has been reported to have 98% to 99% specificity.


Our patient was transferred to us at 33-week gestation when an ultrasound detected anhydramnios. Genetic testing was offered multiple times due to known fetal anomalies, but she declined. Amniocentesis was no longer an option secondary to anhydramnios; however, trisomy 18 was suspected, so prenatal diagnosis for confirmation of diagnosis was recommended. Transabdominal chorionic villi sampling (CVS) was attempted but unsuccessful because only maternal cells were obtained. A relatively new procedure to test the maternal blood for fetal DNA to detect aneuploidy abnormalities was considered a solution. Ultrasound indicated a single umbilical artery, cleft lip, abnormal kidneys, absent bladder, and rocker bottom feet. The patient was counseled regarding the significant risk of neonatal death in the case of trisomy 18 but insisted on full resuscitative measures and a cesarean section for fetal distress. Ironically, she had a Category I fetal monitor strip, and the biophysical profile score was 2/10. Karyotyping of the newborn indicated Turner Syndrome and trisomy 16.


This was our first encounter with transabdominal CVS and fetal DNA testing in maternal blood. We are interested in the impact on the future.