Each year, 450,000 Canadian women become pregnant and, as a result of their participation in prenatal screening for Down syndrome, approximately 10,000 of them will have an amniocentesis (i.e. sampling of liquid surrounding the fetus) and of those, 315 will be found to carry a baby with Down syndrome and 70 normal pregnancies will be lost from complications of the procedure. It has been discovered recently that, during pregnancy, there is fetal DNA in maternal blood in sufficient quantities to be analysed and methods have been proposed to detect the presence or not of a fetus with Down syndrome using maternal blood. The introduction of genomic blood testing as proposed in the context of this project could lead to increased detection of Down syndrome, less invasive screening with 9700 amniocentesis avoided each year in Canada, improving the peace of mind of pregnant women, and preventing the accidental loss of 70 normal fetuses, at a lower overall cost than current practice. However, these methods still need to be validated before being appropriately introduced in routine care.

The study hypothesis is that new genomics-based non-invasive methods using fetal-DNA in maternal blood during pregnancy can be more effective than current prenatal screening methods for fetal aneuploidy.

This project will carry out an independent study that will validate the performance and utility of different new genomic technologies for screening in pregnant women using maternal blood. The team of researchers will compare the real-life performance of different non-invasive assays and strategies to screen for fetal aneuploidy, and identify an evidence-based cost-effective approach for implementation of this new technology in the Canadian health care system. The deliverables of this project will enable decision makers, pregnant women and their partner to make informed choices pertaining to prenatal genetic screening and diagnosis, such as screening for Down syndrome, and reduce the risk to pregnancies associated with amniocentesis.

The present study is a real life comparative effectiveness study that will compare the performances and costs of several prenatal screening modalities for fetal aneuploidy (see interventions).

Inclusion Criteria (High risk arm):

• women 19 years or older between 10 weeks and 23 weeks 6 days gestation undergoing amniocentesis or CVS for:
• positive prenatal screen;
• abnormal ultrasound
• previous pregnancy with trisomy
• patient or partner carrier of Robertsonian translocation involving chr 21
• positive NIPT result
• Maternal age 40 or more

Inclusion Criteria (Low risk arm):

• women 19 years and older who are 10 and 13 weeks 6 days gestation based on dating ultrasound (CRL) and are undergoing screening for Down syndrome (first trimester combined, SIPS or IPS)

Exclusion Criteria:

• women with multiple gestations
• women with twin demise (spontaneous or elective) at any gestational age
• women with active or history of malignancy