Study population
This was a single centre retrospective cohort study conducted between January 2013 and November 2018. The cases were obtained from the ultrasound database at Monash Ultrasound for Women, Melbourne, Australia, which is a dedicated tertiary obstetric and gynaecological ultrasound practice and centre for fetal diagnosis, offering first and second trimester screening for chromosomal and structural anomalies during pregnancy.
All patients were referred by their treating physician for cell-free DNA screening and blood samples were collected onsite. Pre-test counselling was provided, and informed consent was obtained. Women who opted to use NIPT were offered an ultrasound prior to blood sampling to confirm fetal number, viability and gestational age. They were subsequently advised to return for fetal structural assessment between 12 and 13+6 weeks of gestational age.
Further genetic counselling was provided for those patients with fetal oedema on the early scan and the option of either continuing with the planned NIPT or undergoing invasive testing was made after review by an obstetric sonologist in consultation with the referring physician and wishes of the patient. If invasive testing was undertaken, fetal chromosome analysis was performed by fluorescent in-situ hybridization (FISH) plus conventional karyotyping (in cases of abnormal FISH) or microarray analysis (in cases of normal FISH).