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What are prenatal screening tests?
A guide to understandingprenatal screening tests for:• DownSyndrome• Trisomy18• OpenNeuralTubeDefects
Newprenatalscreeningtestsarenowavailableforallwomen.
FORWOMENANDTHEIRFAMILIES
Earlyon inyourpregnancy,youcandecidewhether or not you would like to haveprenatal screening.These testsareoptional- it is your choice whether or not to havethem. The purpose of this Guide is to giveyouinformationtohelpwithyourdecision.
• Thesearebloodtests,sometimeswithanultrasound,whicharedonestartingat11weeks ofpregnancy.• TheyareSCREENINGtests,whichmeanstheytellyouyourCHANCEofhavingababy withDownsyndrome,trisomy18oranopenneuraltubedefect.• Screeningtestscannottellyouforsurewhetherornotyourbabyhasoneofthesethree conditions,onlythechanceofthis.• Tofindoutforsure,youwouldhavetodecidewhethertohaveaDIAGNOSTICtest(see page10).• Prenatalscreeningcannotfindeverybirthdefect.
2 A guide to understanding prenatal screening tests - for women and their families
TheConditions:• DownSyndrome• Trisomy18• OpenNeuralTubeDefects
Downsyndrome*PeoplewithDownsyndromeusuallyhavemildtomoderateintellectualdelay.IndividualswithDownsyndromemayhaveagreaterincidenceofhealthconditionsthantheaveragepersonsuchasheart,stomach, bowel, thyroid, vision and hearing problems. Treatment is available for many of theseconditions.EachpersonwithDownsyndromeisdifferent.Thereisnowaytotesthowseriousthedisabilitieswillbe.PeoplewithDownsyndromegenerallyliveintotheirfifties.Ingeneral,aboutonein1000birthshasDownsyndrome.ThechanceofhavingachildwithDownsyndromeincreaseswiththemother’sage.
Trisomy18*Babieswithtrisomy18havebothmentalandphysicaldisabilities.Manypregnancieswithtrisomy18willmiscarry.Mostbabiesbornwithtrisomy18donotsurvivepastthefirstfewmonthsoflife.Ingeneralaboutonein6,000birthshastrisomy18.Thechanceofhavingachildwithtrisomy18increaseswiththemother’sage.
OpenNeuralTubeDefects*Theseconditionsoccurwhenthebrainorspinalcorddoesnotformproperly.Anopenneuraltubedefectinvolvingthespinalcordiscalledspinabifida.Spinabifidacausesphysicaldisabilitiessuchasdifficultywalking,andcontrollingthebladderand/orbowel.Peoplewithspinabifidamayalsohavementaldisabilities.Treatmentcanhelpwithmanyofthephysicaldisabilities.Anopenneuraltubedefect involving the brain is called anencephaly. A baby with anencephaly will be stillborn or dieshortlyafterbirth.InCanada,thechanceofhavingababywithanopenneuraltubedefectisabout1outofevery2000births.Thechanceofachildbeingbornwiththisconditiondoesnotincreasewiththemother’sage.
* Alistofresourcesonpage11canleadyoutomoreinformationaboutDownsyndrome, Trisomy18orOpenNeuralTubeDefects.
Familyhistory:Othertestsorgeneticcounsellingmaybesuggestedifyouoryourpartnerhaveaclosefamily memberwho was born with a birth defect or has a serious health problem.Pleasetalktoyourhealthcareproviderformoreinformation.
Whatareyourchancesofhavingababywithoneoftheseconditions?
Itisimportanttorememberthatmostbabiesarebornhealthy.
The chance of having a baby with a chromosomecondition like Down syndrome and trisomy 18increaseswiththeageofthemotherasshownintheTablebelow.
Remember…You might decide to have prenatal screening becauseyou want to find out your chance of having a baby withDown syndrome, trisomy 18 or open neural tube defect.This is determined from your age, the blood tests and/orultrasound.
A screening test gives you more information about yourchanceofhavingababywithoneoftheseconditionsthanthechanceshowninthetableabove.
Everywoman,nomatterwhatage,hasa2-3%chance(2or3chancesin100)ofhavingababywithsomekindofbirthdefect.Birthdefectscanincludeconditionslikeheartproblemsandextratoes.
Mother’sage(years)
20
25
30
35
40
45
ChanceofDownsyndrome
1in1,650
1in1,250
1in950
1in385
1in100
1in30
Chanceofanychromosomeconditionincludingtrisomy18,DownSyndromeandothers
1in530
1in480
1in390
1in180
1in65
1in19
3
Chanceofchromosomeconditionswithvaryingmaternalage:
ArePrenatalScreeningTestsrightforyou?
Manywomenhaveadifficulttimedecidingwhetherornottohaveprenatalscreeningtests.SomewomenfindithelpfultoreadallofthisGuidefirst,beforemakingadecision.
Remember,itisyourchoicewhetherornottohaveaprenatalscreeningtest.
Herearesomethingstothinkaboutthatmighthelpyoumakeyourdecisionandmaybediscusswithyourpartner,healthcareprovider,familyorfriends.
1. DoyouwanttoknowthechanceofyourbabyhavingDownsyndrome,trisomy18oropenneural tubedefect? •ThereisnocureforDownsyndrome,trisomy18oropenneuraltubedefect. •Ifoneoftheseconditionsisfound,yourhealthcareprovidermaysuggestadditionaltestsand/or changeinthewayyourbabyisdelivered. •Somepeoplehavescreeningbecausetheywouldliketheinformationbeforebirth,orwouldliketo prepareforachildwithspecialneeds. •Somepeoplehavescreeningbecausetheywouldconsidergivingthebabyupforadoptioniftheir babywasfoundtohaveoneoftheseconditions. •Somepeoplehavescreeningbecausetheywouldhaveanabortioniftheirbabywasfoundtohaveone oftheseconditions.
2. Howwillthisinformationaffectyourfeelingsthroughoutyourpregnancy? •Manywomenworryiftheirtestresultssaythatthechanceofhavingababywithoneofthese conditionsishigherthanexpected(calledscreenpositiveseepage8).
3. Ifyourscreeningtestresultsaysthechanceishigherthanexpected(calledscreenpositiveseepage8), youwillneedtodecideifyouwantdiagnostictesting(seepage10)tofindoutforsureifyourbabyhas Downsyndrome,trisomy18oropenneuraltubedefect.
4. Diagnostictestingwilltellforsureifyourbabyhasoneoftheseconditions,buthasasmallchanceof miscarriage.Areyouwillingtotakethatrisk?Forinformationaboutdiagnostictestingseepage10.
5. Ifmoretestingshowsyourbabyhasaconditionforsure,whatwillyoudowiththeinformation? Youwillneedtodecideifyouwanttocontinuethepregnancyorhaveanabortion.
6. IfyoufindoutforsurethatyourbabyhasaconditionlikeDownsyndrome,youcanplanforthe birthofyourchildandfindoutfromotherswhatitisliketoraiseachildwiththiscondition.Would thisinformationbehelpfultoyoubeforebirth?Remember,toknowforsureyouhavetohavea diagnostictestwhichhasasmallchanceofmiscarriage.
7. Ifyouhaveachildwithmentaland/orphysicaldisabilities,howmightthisaffectyourlife,yourother children,yourrelationshipwithyourpartnerandyourextendedfamily?
4 A guide to understanding prenatal screening tests - for women and their families
Otherthingstothinkabout:•ScreeningtestswillfindmostbabieswithDownsyndrome,trisomy18oropenneural tubedefects,butnotall.Formoreinformationseepage8.•Screeningtestswillnotfindeverykindofbirthdefect,notestcandothis.•PrenatalscreeningtestsmightalsofindconditionsotherthanDownsyndrome, trisomy18andopenneuraltubedefectsbutthesearethecommonest.
5
Doyouwanttohaveprenatal screening or not?
Thechoiceisyours.
Decisionsyoumayneedtomake:IfyouareUNDECIDEDaboutprenatalscreening:YoumaywanttoreadallofthisGuidebeforemakingadecision.Youcandiscussyouroptionswithyourhealthcareproviderorgeneticcounsellor.Youcanhaveprenatalscreeningandmakeachoicewhetherornottocontinuetheprocessateachstep.
IfyoudecideYEStoprenatalscreening:
Youwillneedtodecidewithyourhealthcareproviderwhichprenatalscreeningtestisrightforyou(seepage6)
If your prenatal screening test is screenPOSITIVE, you will need to decide if youwillhavediagnostictesting,keepinginmindthatthereisasmallriskofmiscarriage.
IfyoudecideYEStodiagnostictesting:Youwillneed todecidewhatyouwilldo if the result shows your baby hasoneoftheseconditions.Willyouhavean abortion? Will you continue thepregnancy?Willyougivethebabyupfor adoption?
IfyoudecideNOtoprenatalscreening:
Youmayhavedecidedthatyoudon’twanttoknowifyourbabyhasoneoftheseconditions,youwouldpreferto“takewhatcomes”.
Youmayhavedecidedthatyouwouldnotwanttohaveadiagnostictestunderanycircumstancesbecauseofthesmallchanceofmiscarriage.
Youmayhavedecidedthatyouwouldnothaveanabortionifdiagnostictestingconfirmedthatyourbabyhadoneoftheseconditions.
Ifyouareover35yearsofageatyourduedate:
•Youneedtodecideifyouwouldprefer diagnostictestingwhichcantellforsureif yourbabyhasoneoftheseconditionsbuthas ariskofmiscarriage,or…
•Ifyouwouldprefertohaveprenatalscreening firstandmakeadecisionaboutdiagnostic testingdependingonthescreeningtestresults.
Forwomenover35years of age at their due date:Women35yearsofageandoverattheirduedatecandecidenottohaveaprenatalscreeningtestbutgodirectlytodiagnostictestingsuchasCVSandamniocentesis.Rememberthatscreeningtestsgiveabetterestimateofriskthanagealone,forthoseaged35to39.Inparticular,women40andovershouldconsidercounsellingabouttheprosandconsofscreeninganddiagnostictesting.Formoreinformationaboutdiagnostictestingseepage10andtalktoyourhealthcareprovider.
Insomeareas,thishaschangedandappliestowomen 40yearsofageandoverattheirduedate.
IhavedecidedthatIwanttohaveprenatalscreening,nowwhat?Youneedtochooseaprenatalscreeningtestwithyourhealthcareprovider.Thefollowingtablewillhelpyouunderstandthedifferentprenatalscreeningtests.
Test/Procedure
1stbloodsample
Nuchaltranslucencyultrasound
2ndbloodsample
Resultsavailableat:
Detectionrate(Accuracy)
Falsepositiverate
Diagnostictestifprenatalscreeningtestispositive
Diagnostictestresultsavailableat:
Abortion–ifyoudecidetohavethis–couldbeperformedat:
Or:Continuationwithpregnancy
FirstTrimesterScreening(FTS)
11-14weeks
11-14weeks
NONE
12-15weeks
Ofevery100pregnancieswithDownsyndrome,about80-85willbedetected(80-85%)
About3to9outof100pregnancies(3-9%)
CVS11-13weeksIfCVSisnotavailable,youcouldhaveamniocentesisdiagnostictestingasdescribedinthenextcolumn➔
13-15weeks
13-23weeksAbortiontimingwilldependonlocalavailability
Birth
IntegratedPrenatalScreening(IPS)
11-14weeks
11-14weeks
15-20weeks
16-21weeks
Ofevery100pregnancieswithDownsyndrome,about85-90willbedetected(85-90%)
About2to4outof100pregnancies(2-4%)
Amniocentesis15-22weeks
17-24weeks
17-23weeksAbortiontimingwilldependonlocalavailability
Birth
SerumIntegratedPrenatalScreening(SIPS)
11-14weeks
NONE
15-20weeks
16-21weeks
Ofevery100pregnancieswithDownsyndrome,about80-90willbedetected(80-90%)
About2to7out of 100pregnancies(2-7%)
Amniocentesis15-22weeks
17-24weeks
17-23weeksAbortiontimingwilldependonlocalavailability
Birth
Ifyourfirstvisitwithyourhealthcareproviderisbefore14weeks(3-1/2months)ofpregnancy:• Youcanhaveoneofthenewprenatalscreeningtests:FirstTrimesterScreening, IntegratedPrenatalScreeningorSerumIntegratedPrenatalScreening.• Thestepsinvolvedineachofthesetestsandtheiraccuracyaredescribedinthetablebelow.
NuchalTranslucency(NT)ultrasoundisavailableinmostmid-sizeorlargercities.Ifyouliveinanareawherethisspecialultrasoundisnotavailable,youcanstillhaveSIPS.
NuchalTranslucencyisafluid-filledspaceatthebackofeverybaby’sneck.Anultrasoundtomeasure thisisdonebetween11and14weeksofpregnancy.Thechanceofacondition,likeDownsyndrome,is higherwhentheNTmeasurementislargerthanexpected.
FTSofferstheearliestavailableresultsbutrequiresabloodtestforneuraltubedefectslaterinthepregnancy.
FTSisnotavailableinallcommunities.Pleasecheckwithyourhealthcareprovider.
IPSandSIPSarealittlemoreaccuratethanFTSandincludescreeningforneuraltubedefects,butthisisa2-stepprocessand
resultsareavailablelaterinthepregnancy.
6 A guide to understanding prenatal screening tests - for women and their families
7
Ifyourfirstvisitwithyourhealthcareproviderisafter14weeks(3-1/2months)ofpregnancy:• YoucanhaveTripleorQuadrupleprenatalscreening.Inmostareastriplescreeninghasbeenreplaced byquadruplescreeningbecauseitisalittlemoreaccurate.
• Thestepsinvolvedineachofthesetestsandtheiraccuracyaredescribedinthetablebelow.
Test
Bloodsample
Resultsavailableat:
Detectionrate(Accuracy)
Falsepositiverate
Diagnostictestifprenatalscreeningtestispositive
Diagnostictestresultsavailableat:
Abortion–ifyoudecidetohavethis–couldbeperformedat:
Or:Continuationwithpregnancy
TripleScreening
15-20weeks
16-21weeks
Ofevery100pregnancies withDownsyndrome,about70willbedetected(70%)
About7outof100pregnancies(7%)
Amniocentesis15-22weeks
17-24weeks
17-23weeksAbortiontimingwilldependonlocalavailability
Birth
QuadrupleScreening
15-20weeks
16-21weeks
Ofevery100pregnancies withDownsyndrome,about75to85willbedetected(75-85%)
About5to10outof100pregnancies(5-10%)
Amniocentesis15-22weeks
17-24weeks
17-23weeksAbortiontimingwilldependonlocalavailability
Birth
Howaccurateareprenatalscreeningtests?
DownsyndromeThedetectionandfalsepositiveratesinthetableonlyrefertoDownsyndrome.Thisisbecausetrisomy18israreandwedonothaveexactnumbersforit.
Trisomy18Generally,forallofthetestslisted,thedetectionrateoraccuracyislessfortrisomy18thanwhatitisforDownsyndrome.Saidanotherway,thesetestsarenotquiteasgoodatmeasuringthechanceofhavingababywithtrisomy18(detectionrate)asmeasuringthechanceofhavingababywithDownsyndrome.
OpenneuraltubedefectsScreeningforopenneuraltubedefectsconsistsofabloodtestdonebetween 15-20 weeks. This is done as part of IPS, SIPS, Quad orTriplescreeningorasanadditionalbloodtest ifawomanishavingFTS. The ultrasound done at about 18 weeks of pregnancy alsogives information about open neural tube defects. Of every 100pregnancies with an open neural tube defect, 80 (or 80%) will bedetectedwithprenatalscreening.
Rememberthatmostbabiesarebornhealthy.
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
8 A guide to understanding prenatal screening tests - for women and their families
Understandingyourresults:
This is a picture of the results if 1000 women have IntegratedPrenatalScreening.Forexample,if1,000womenofanyagehaveIntegratedPrenatalScreening,between20and40(or2-4%)willhavea“screenpositive”resultforDownsyndrome.Thismeans they are at increased risk of having a baby with Down syndrome. If all ofthosewomenhavediagnostictesting(seepage10)tofindoutforsureiftheirbabieshaveDownsyndrome,onlyoneofthemwillbefoundtohaveababythatactuallyhasDownsyndrome.
This is explained in the chart. Each circle represents 1 pregnant woman who hadIntegratedPrenatalScreening(IPS).Thereare1,000pregnantwomen(circles).
SCREENNEGATIVEO Circles represent women whose prenatal screening result will be screennegative for Down syndrome. 960 to 980 women out of 1,000 will have ascreennegativeresult.
FALSEPOSITIVERESULT Circlesrepresentwomenwhoseprenatalscreeningresultisscreenpositivefor
Downsyndrome.19to39womenoutof1,000willhaveafalsepositiveresultandwillhaveababythatdoesnothaveDownsyndrome.
TRUEPOSITIVERESULT Circlerepresentsatruepositiveresult.About1womanoutof1,000willhave
atruepositiveresult–ababywhohasDownsyndrome.
Outof100pregnancieswithDownsyndrome,IPSwillfind85to90,andwillmiss10to15.
Rememberthatabout1pregnantwomanin1,000willhaveababywithDownsyndrome.
Ifyourresultisscreenpositive,youcantalktoyourhealthcareprovideraboutmoretesting.Diagnostictesting(page10)isnecessarytotellifyourbabyhasaconditionforsure.Ifyourresultisscreenpositiveforaneuraltubedefect,youmayhavetheoptionofadetailedultrasoundat18to20weeksinsteadofamniocentesis-thiswillvarydependingonwhereyoulive.Geneticcounsellorsareavailabletodiscussyourtestresults.Theycanhelpyoumakeadecisionaboutdiagnostictesting.Theywillsupportyourdecisionnomatterwhatyoudecide.
Ifyourscreeningtestresultisscreenpositiveandtestingsaysthebabyhastheconditionforsure,youwillbeaskedifyouwanttocontinuethepregnancyorhaveanabortion.Geneticcounsellorsareavailabletodiscusswhatyourresultsmeanandyourchoices.Youdon’thavetodecidebeforetestingwhatyouwoulddo.Yourhealthcareproviderwillalsodiscussyourchoiceswithyou.Youmaywanttodiscussthiswithyourpartner,friendsorfamily.
Rememberthatmostbabiesarebornhealthy.
9
What if they tell me my screening result isSCREENNEGATIVE?
The chance of your baby having Downsyndrome, trisomy 18 or open neuraldefectisLOWERthanexpected.
Is a SCREEN NEGATIVE resultaccurate?
There is less than a 1 in 1,000chanceofyourbabyhavingDownsyndromethatwasnotidentifiedbythescreeningtest.
Whenyourbabyisborn,ifheor she does not have any ofthese conditions, your resultwasaTRUENEGATIVE.
Understandingyourresults:Whentheytellmemyresult,howwillIknowwhatitmeans?
What if they tell me my screening result is SCREENPOSITIVE?
The chance of your baby having Down syndrome,trisomy18oropenneuraltubedefectisHIGHERthanexpected.
IsaSCREENPOSITIVEresultaccurate?Most screen positive results turn out to befalse,eitherbydiagnostictestingorthebirthofababywhodoesnothaveDownsyndrome,trisomy18oropenneuraltubedefect.ThisiscalledaFALSEPOSITIVE.
What ifaSCREENPOSITIVEresult isnotfalse?
About1outof1,000womenwillhaveaTRUEPOSITIVEresult,whichmeansthatafterdiagnostictestingorbirth,thebabydoeshaveDownsyndrome,trisomy18oranopenneuraltubedefect.
Every pregnancy has 2 or 3 chances in100(2-3%)ofhavingaconditionthatisnotfoundbyprenatalscreeningtests.
Itisimportanttorememberthatnotestcandetecteverytypeofbirthdefect
Diagnostictests
YouhavealreadylearnedthatscreeningtestscantellyouyourchanceofhavingababywithDownsyndrome,trisomy18andopenneuraltubedefects.
Diagnostictestscantellforsureifyourbabyhasoneoftheseconditions.Thesediagnostictestsareavailableonlyifyourscreeningtestresultispositiveorifyouare35yearsofage(insomeareas,thishaschangedto40yearsofage)orolderatyourduedateandincertainothersituations.
ChorionicVillusSampling(CVS)CVSisatestwhichtellsforsureifyourbabyhasDownsyndromeortrisomy18.Thistestisusuallydonebetween 11and 13weeksofpregnancy.Usingultrasound,a smallpieceof tissue is removedfromtheplacentafortesting,usuallythroughthevagina,butsometimesthroughtheabdomen.Anywomancanhaveamiscarriageatthistimeofpregnancy.IfshehasCVS,thisriskisincreasedbyanextraonein100(1%).Theresultisavailablein2-3weeks.Formoredetails,discussCVSwithyourhealthcareprovider.CVSisnotavailableinallareas.
AmniocentesisThistestcantellforsureifyourbabyhasaconditionlikeDownsyndromeortrisomy18.Sometimesitisusedtotellifyourbabyhasanopenneuraltubedefect.Thetestisusuallydonebetween15and22weeksofpregnancy.Usingultrasound,aneedleisinsertedthroughtheabdomenintothefluidaroundthebabyandasmallamountofamnioticfluidiswithdrawn.Theneedledoesnottouchthebaby.Anywomancanhaveamiscarriageatthistimeofpregnancy,but,ifshehasamniocentesis,thisriskisincreasedanextra1in400(0.2%).Newstudieshaverecentlyshownthattheriskofmiscarriagemaybeevenlower,possiblyaslowas1in1,600(0.06%).Theresultsareavailablein2-3weeks.Formoredetails,pleasetalktoyourhealthcareprovider.
Mosttimes,amniocentesisorCVSwillshowthatyourbabydoesnothaveDownsyndrome,ortrisomy18,butthesetestscannotfindeverycondition.Evenafteranormalresult,thereisachanceofhavingababywithadifferentconditionsuchasaholeintheheartormentaldisability.
Rememberthatmostbabiesarebornhealthy.
Awordaboutunexpectednews:Ifyouhavediagnostic testingandtheresultsconfirmthatyourbabyhasDownsyndrome, trisomy18oropenneuraltubedefect,geneticcounsellorsareavailabletohelpyoudiscussyouroptions:continuingthepregnancy,adoptionorhavinganabortion.Makingadecisionisnoteasy.Geneticprofessionalscanhelpwithfindingresourcessuchassupportgroups,thatmaybehelpfultoyouduringandafteryourdecision-making.Therearehealthcareprovidersavailabletohelpyouandoffersupportnomatterwhatdecisionyoumake.
Thechoiceisyours.
10 A guide to understanding prenatal screening tests - for women and their families
Additionalsourcesofinformation:
CanadianAssociationofGeneticCounsellors:http://www.cagc-accg.caor905-849-8299ListofmedicalgeneticcentreslocatedacrossCanada.
CanadianDownSyndromeSociety:http://www.cdss.caor1-800-883-5608MoreinformationaboutDownsyndromewithlinkstolocalparentsupportgroups.
TheGeneticsHomeReference-YourGuidetoUnderstandingGeneticConditions:http://www.ghr.nlm.nih.govAnexcellentsitetolearnmoreaboutgeneticsincludingDownsyndrome,trisomy18andmore.
MarchofDimes:http://marchofdimes.com/Excellentsourceofinformationaboutpregnancyincludingcommonprenataltests,complicationsduringpregnancy,thingstoavoidduringpregnancy,birthdefectsetc.
Motherisk:http://www.motherisk.org/or416-813-6780or1-877-327-4636Information service for women who have been exposed to environmental agents, drugs and alcoholduringpregnancy.
OntarioMultipleMarkerScreening(MMS)Program:http://www.lhsc.on.ca/programs/rmgc/mss/Informationonprenatalscreeningtests.
S.O.F.T.SupportOrganizationForTrisomy18,13andRelatedDisorders:http://www.trisomy.orgor1-800-716-7638or585-594-4621Moreinformationabouttrisomy18.
SpinaBifidaandHydrocephalusAssociationofCanada:http://www.sbhac.caor1-800-565-9488Moreinformationaboutspinabifida.
11
The Genetics Education Project
TheGeneticsEducationProjecthttp://www.mtsinai.on.ca/FamMedGen/TodownloadacopyofthisGuide.
©August2007
Prenatalscreeningtimeline:
Whenwouldyourscreeningtesthappen?
If your prenatal screening test shows an increased chance of Downsyndrome,trisomy18oropenneuraltubedefectsyoumaydecidetohavediagnostictesting.Informationaboutdiagnostictestingisalsoavailableinthisguide.
12 A guide to understanding prenatal screening tests - for women and their families
Blood testand Ultrasound
RESULTSAVAILABLE
You are pregnant
Weeks11-14
Weeks12-15
Weeks15-20
Weeks16-21
FirstTrimesterScreening
(FTS)
Blood testand Ultrasound
Secondof2bloodtests
RESULTSAVAILABLE
IntegratedPrenatal
Screening(IPS)
Firstof2bloodtests
Secondof2bloodtests
RESULTSAVAILABLE
SerumIntegratedPrenatal
Screening(SIPS)
Blood test
RESULTSAVAILABLE
Tripleand
QuadrupleScreening