• Genetic Screening: FAQ

The goal of prenatal screening is to gather as much information as possible in order to optimize outcomes. It is very important to remember that almost all are healthy ones; however, a small minority of pregnancies is affected by problems with the egg prior to fertilization, or problems with the developing embryo or . The goal of is to identify these few pregnancies, but an unfortunate side effect of this type of screening can be anxiety. Some of the problems which may be detected include:

• Genetic Disorders The most common genetic disorders are imbalances of the major pieces of material which hold genes, known as chromosomes, resulting in an embryo with an extra chromosome. This condition is called Trisomy, and the most common is Trisomy 21, or . Down Syndrome impacts the brain, heart, kidneys, spine, and stomach, ranging in effect from very mild to very severe. Trisomy 13 and 18 are two other chromosome imbalances that are incompatible with life. This means they can only survive in utero until birth or for a shirt while afterwards. The risk of chromosome imbalances is determined individually based on the woman’s age. • Spinal Cord Defects Spinal cord defects, such as spina bifida or anencephaly, are rare in the general population (1:1000). However, the testing is relatively simple (a blood test at 16-18 weeks and a detailed at 19-20 weeks) to look at the fetal spine and brain. • Placental Disorders There is growing evidence over the last several years that placental function is the cause of severe fetal-maternal complications such as growth restriction, and severe hypertension in pregnancy. One non-genetic spin off from first trimester screening is the reporting of PAPP-A, a protein made from the placenta. In placental disorders, the PAPP-A is in low amounts in the maternal blood system, and this may be a marker for problems in later pregnancy. It is a way to be able to screen for such problems. • Defects of Anatomy Anatomic defects are generally non-genetic in origin. Problems such heart defects, spinal defects, and facial defects are best seen at the anatomic ultrasound at 18-20 weeks of pregnancy.

What tests are offered? The screening test that is available to you depends on your age at your due date; older women are offered more tests and younger women are offered less. Please see the reverse of this handout for the details about the various genetic tests available to you.

What if a screening test is positive? If a screening test, such as the TMS, gives a “positive” result, it simply means that you are at elevated risk; it does not mean that your baby necessarily has any of these conditions. At this point, you will be offered an to give you a diagnosis. You can accept or decline the amnio as you wish.

What if a diagnostic test is positive? If a diagnostic test, such as amniocentesis is positive, it means that your baby is indeed affected by the identified condition. At this point, you will be offered the option of terminating the pregnancy, which of course you can accept or decline as you wish.

Do I have to have this testing? Absolutely not. Genetic testing (such as the TMS) and prenatal screening (such as a detailed ultrasound at 19-20 weeks) are offered to every woman in BC, but the choice is yours as to whether you would like any or all of these tests. Most women do them, but there are many who do not. It is a personal decision. Feel free to talk to your about the options that are right for you.

Triple Marker Chorionic Villlus Amniocentesis Serum Integrated Integrated Prenatal First Trimester Screening (TMS) Sampling (CVS) Prenatal Screen Screen (IPS) Screen (FTS) Provided for client use by The Midwifery Group, Vancouver, BC, www.midwiferygroup.ca This information is not intended to substitute for the trained guidance of your caregiver. Please check with your whenever you are uncertain about any information.

(SIPS) Who is All women Age over 35 -Age over 35 Age over 38 -Age over 40 Willing to pay privately eligible? -Age over 32 + twins -Previous child with Trisomy ($500) -Previous child with 13 or 18 or Down Syndr. Done at PCRM clinic in Down Syndrome or -Age over 35 + 3 previous Burnaby, Genesis clinic Trisomy 13 or 18 miscarriages in Vancouver -HIV positive Kind of test One blood test from Sample of cells from Sample of cells in Two blood tests from Two blood tests from One blood test from mother placenta (taken via (taken mother mother plus measurements mother plus the or via a needle through of fetus via ultrasound measurements of fetus abdomen) the abdomen) via ultrasound When Between 10+3 to 12+6 weeks >15 weeks Part 1: 10 to 13+6 Part 1: 10 to 13+6 weeks, Blood test: 11 to 13+6 15 and 20+6 wks weeks Ultrasound: 11 to 14 weeks, weeks Part 2: 15 to 20+6 Part 2: 15 to 20+6 weeks Ultrasound 12 to 14 weeks weeks Screens for Chromosomal Chromosomal Chromosomal Chromosomal Chromosomal abnormalities Chromosomal abnormalities (Down abnormalities abnormalities (Down abnormalities (Down (Down Syndrome and abnormalities (Down Syndrome and (Down Syndrome Syndrome and Syndrome and others), others), Spina Bifida Syndrome and others) others), Spina Bifida and others) via others), Spina Bifida Spina Bifida placental sample, Spina Bifida via blood sample at Quality of Screening Diagnostic Diagnostic Screening Screening Screening results Results by 10-14 days after test, 2-3 weeks after 2-3 weeks after test, 10-14 days after Part 2 10-14 days after Part 2 Same day as u/s, usually by 17 weeks test, usually by 14 usually by 18 weeks complete, usually by 17 complete, usually by 17 usually by 12 weeks weeks weeks weeks Detection rate Overall: 70% 98-99% 99.4% 90% (if >38 years) 90-95% (if >40 years) 90-95% for Down (~90% if >35 years of Syndrome age) False positive Overall: 7-8% 1% 0.1% 19% if >38 years 13% if >40 years 4-5% rate 29% >38 years 30% if >40 years 37% >40 years False negative ≈0.1% ≈0.01% ≈0.0001-0.001% ≈0.1% ≈0.1% ≈0.01-0.03% rate Risk of None 1-2/100 (1-2%) 1-2/200 (0.5-1%) None None None pregnancy loss Options if Ultrasound to confirm Genetic counseling Genetic counseling Genetic counseling Genetic counseling positive EDD Amniocentesis Termination Amniocentesis Amniocentesis Amniocentesis Genetic counseling Nothing Nothing Nothing Nothing CVS Amniocentesis Nothing Nothing Advantages Non-invasive Early Detection Diagnostic = no Non-invasive Non-invasive Early detection More accurate than chance of false Higher detection rates Best detection with lowest age alone positive or false & lower false positives chance of false positives negative than TMS Disadvantages Chance of false Risk of pregnancy Risk of pregnancy Chance of false positive Chance of false positive Chance of false positive positive loss loss Chance of false Chance of false positive positive

Provided for client use by The Midwifery Group, Vancouver, BC, www.midwiferygroup.ca This information is not intended to substitute for the trained guidance of your caregiver. Please check with your midwife whenever you are uncertain about any information.