|Public Information Health Care Providers News Media Text Only Version|
Ontario Prenatal Screening
(Multiple Marker Screening Program)
Prenatal Screening Tests for the Detection of:
Advances in prenatal screening have resulted in new tests that offer an improved detection rate and fewer false positives in the detection of chromosome abnormalities. These include nuchal translucency (NT) ultrasound, and new biochemical markers (PAPP-A and DIA). Timing of these tests beginning at 11 weeks’ gestation requires discussion early in pregnancy.
What disorders are being screened for?
Prenatal screening gives a woman her individual risk of having a child with Down syndrome, trisomy 18 and open neural tube defects. It does not screen for all chromosome abnormalities, so some may be missed. Following positive results, women will need to decide whether to go on to have diagnostic testing (i.e. CVS or amniocentesis). Prenatal screening should be offered as part of a program where diagnostic testing, counselling and follow up are available.
Down Syndrome (trisomy 21):
Down Syndrome characteristics include: intellectual disability of varying severity, characteristic facial appearance, hypotonia & other less common congenital anomalies. The general population incidence of Down syndrome is about 1 in 1000, but varies with maternal age.
Prenatal ultrasound findings: congenital heart defects (40%), intestinal obstruction (12%). Approximately 1/3 of affected fetuses will have normal ultrasounds at 18-20 weeks.
Trisomy 18 (Edwards syndrome):
95% of pregnancies with trisomy 18 will result in a miscarriage or stillbirth, and 95% of these liveborn infants die by 1 year. Surviving infants will have severe intellectual disabilities and multiple congenital anomalies. The general population incidence of trisomy 18 is 1 in 6,000, but varies with maternal age.
Prenatal ultrasound findings: congenital heart defects (90%), choroid plexus cysts, distinct hand posture, club feet, micrognathia, intrauterine growth retardation and others. Though rare, affected fetuses may have a normal ultrasound at 18-20 weeks.
Open Neural Tube Defects (NTD) - including anencephaly and spina bifida:
Anencephaly is lethal. Most babies with spina bifida survive and may have problems ranging from hydrocephalus, paralysis and learning/intellectual disabilities to no physical or mental disabilities. Non-gestational diabetes mellitus, anticonvulsant medications, family history of NTD and hyperthermia result in a higher chance of an affected child. The general population incidence in North America is about 1 in 2,000, and does not vary with maternal age.
Things to keep in mind:
Call the ministry INFOline at 1-866-532-3161
| central site
| contact us
| site map
| français |