P849: Meiotic recombination on display through preimplantation genetic testing for two X-linked disorders

Case 2: A 36yo (G8P6016) was noted to have NIHF including large cystic hygroma, abdominal ascites, pleural effusion, and generalized edema at 15w3d.A single umbilical artery, oligohydramnios and abnormal position of the fetal legs was also identified.Chromosomal microarray on placental biopsy was normal female.Maternal TORCH titers were non-contributory.Subsequently, trio exome sequencing identified a de novo heterozygous pathogenic variant in USP7 [c.383+1G>C p.?].Pregnancy was terminated and autopsy was not performed.Case 3: A 33yo (G7P3033) was noted to have NIHF with skin edema, bilateral pleural effusion, and ascites at 16w6d.Additional findings included bilateral loculated cystic structure on the fetal neck, armpits and groin, as well as an anechoic cystic fluid collection within the fetal buttocks.Growth restriction (<1%) and echogenic bowel were also seen.Fetal demise was noted at 17w6d.Cytomegalovirus, parvovirus and toxoplasmosis PCRs on amniotic fluid were negative.Chromosomal microarray on amniotic fluid showed a female fetus with a 358 kb duplication of 16p13.2,including partial duplication of USP7, classified as a variant of uncertain significance.Proband only exome sequencing was negative; however, CNV analysis was not performed due to suboptimal data.Parental testing for the duplication was declined.Autopsy confirmed the ultrasound findings and noted low set ears; and short, broad nasal root with transverse skin crease.No internal malformations were identified.