Sacrococcygeal teratoma is a rare neoplasm that arises from a totipotent stem cell in Henson’s node. It has rarely been associated with chromosomal abnormalities. We present a unique case of a 25-year-old primigravida at 19 weeks and 5 days of gestation found to have an exophytic complex mass with cystic and solid components in the sacral region. This mass was consistent with a sacrococcygeal teratoma. The patient had originally declined genetic screening. After the ultrasound and genetic counseling, she opted to have cell-free fetal DNA screening that was positive for Trisomy 13. Amniocentesis was performed to confirm the diagnosis. The karyotype demonstrated an abnormality of chromosome 13 and microarray demonstrated a complex structural abnormality of chromosome 13 with large regions of copy number gain. The patient underwent a dilation and evacuation at 23 weeks and 2 days. No fetal autopsy was done. This is a case of a prenatally diagnosed sacrococcygeal teratoma associated with Trisomy 13. It illustrates the diagnostic importance of amniocentesis in setting of fetal anatomical abnormalities on ultrasound. For patients who are reluctant to undergo amniocentesis, cell-free DNA results may provide the additional evidence of the need for diagnostic tests.

We present a case of isolated fetal ascites diagnosed at 20 weeks’ gestation. No aetiology was identified on extensive prenatal workup, including prenatal microarray. The patient terminated the pregnancy at 23 weeks’ gestation. Exome sequencing was performed on the products of conception, which ended up giving insight into a possible cause for the ascites. Two heterozygous missense variants of uncertain significance were identified in the PIEZO1 gene. The paternal variant has been linked to dehydrated hereditary stomatocytosis. The father of the baby suffers from haemolytic anaemia, splenomegaly and has had jaundice throughout his life. His brother and father have similar conditions. We suspect that at least one of the gene variants identified in our exome sequencing may be responsible for the illness that runs in this family, including the fetus with isolated ascites.

Background Fetal lateral neck cysts are transient fluid accumulations that result from abnormal lymphatic formations. In the first trimester, fetal lateral neck cysts accompanied by an increased nuchal translucency have been associated with aneuploidy, single-gene disorders and other malformations. Highlights We describe a case in which a lateral neck cyst, which measured 6.7 × 4 × 6.2 mm, was detected by ultrasonography in the first trimester with the additional finding of increased nuchal translucency (3.7 mm; >95th percentile). No other abnormalities were detected at that time. Standard cell-free DNA screening resulted in no aneuploidy detected for chromosomes 21, 18, 13 and the sex chromosomes. The patient declined diagnostic testing with chorionic villus sampling. A repeat ultrasound at 16 weeks’ gestation demonstrated a normally grown fetus with persistence of the cyst, which measured 4.9 × 5 × 8.4 mm, as well as a pericardial effusion with a single outflow tract overriding the ventricular septum and vermian hypoplasia. The diagnosis of trisomy 9, 47,XX,+9, was made by amniocentesis and the patient opted for termination of the pregnancy. Conclusions This report illustrates the importance of identifying additional abnormalities in a fetus with lateral neck cysts, documenting the size of the cysts and obtaining diagnostic genetic testing.