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).