P864: Challenges of genetic counseling in prenatal setting: Follow up of a child born after conspicuous result for Pallister Killian syndrome

patient noted a family history of AIS.All four sisters have a diagnosis of AIS, normal female external genitalia, an XY karyotype, and had surgical removal of the testes.There was no suspicion or diagnosis of AIS in any other of the patient's maternal family members.No family members have pursued genetic testing for pathogenic variants of AIS.The patient had no symptoms of AIS and has a 46,XX karyotype, indicating she does not have AIS but may be a heterozygote.Diagnostic Workup: At 13 weeks gestational age, the patient underwent in-house cfDNA screening resulting in a fetal fraction of 10.5% with low risk for trisomies 21, 18, and 13 and a result consistent with a single X and Y chromosome.An initial ultrasound at 14 weeks gestational age noted a viable singleton pregnancy with no abnormal findings.At 21 weeks gestational age, ultrasound showed no abnormal findings and normal fetal external female genitalia.However, the presence of normal fetal external female genitalia contradicted the previous cfDNA screening results of an XY chromosomal complement.Along with the family history of AIS, this suggests that the fetus has AIS.