Fetal Diagnostic Testing (unit 3) Flashcards
diagnostic testing
- used to evaluate fetus for genetic/congenital disorders
* genetic screening, amniocentesis, etc
antepartum testing
- done AFTER problem is detected and goal is to evaluate how fetus is tolerating
- NST, kick counts, U/S, etc
ultrasound
•produces image based on echos
•visualization of fetus and surrounding structures
•dark spots= fluid
•white spots= tissue
•transabdominal or transvaginal
*need full bladder for transabd. if < 20 wk
best U/S for viewing internal organs
•2D
biggest risk of U/S
•missing something
benefit of 3D U/S
•identifying cleft lift and palate
standard U/S
•general survey of fetus, amniotic fld.
specialized U/S when…
•abnormalities exist on basic U/S
•MSAFP
*hx of congenital abnormality
limited U/S when…
- need specific info needed
- emergency
- testing BPP, AFI, fetal weight, fetal position, confirmation of cardiac activity
1st trimester U/S
•transvaginal- uterus, gest. sac (6-8 wk), embryo •used to -detect ectopic (transvag) -multifetal -confirmation (FHR @ 6-7 wk) -gestational age (BPD)
2nd trimester U/S
*standard U/S •trasnabdominal •confirm GA/fetal viability •evaluate fetal anatomy •locate placenta •detect congenital abnormalities •assist w/ PUB or amnio
3rd trimester U/S
- confirm viability
- detect macrosomia/IUGR
- fetal position
- AFV, fetal breathing/activity
- amnio or BPP
fetal sex determination via U/S
•after 18 wks
GA assessment via U/S
•most accurate if done early (1st trimester)
how does 2nd trimester U/S compare to LMP
•not very accurate at that point b/c there can be a difference of 1-2 wks
when is crown to rump embryo length most accurate
•7-12 wk
positioning U/S
- wedge under hip in late trimesters
* lithotomy for transvag
screening tells us…
•there is a RISK of an issue
diagnostic tells us…
•there IS an issue
Alpha-Fetoprotein Screening (MSAFP)
•fetal liver protein (AFP) produced in predictable amnt. until 20 wks
•maternal serum tested for anomolies @ 16-18 wks
*key mom blood determinant screening
MSAFP anomalies
- 80% open NTD and open abd wall defects
* 33% trisomy 21
factors that influence MSAFP results
- GA (validity affected if really off on dates)
- maternal weights
- race
- maternal dz
what does MSFP detect
- spina bifida
* ancephaly
anecephaly
- no brain
- folic acid supp prevent
- 95% fatal
- organ donor
triple marker test
- MSAFP+hCG+Estriol
- 80% detection ONTD
- 60% detection trisomy 21
- 50% detection trisomy 18
quad screen
•maternal AFT (fetal liver protein)
•hCG (placenta hormone)
•unconjugated estriol (uE3)- fetus/placenta protein
•inhibin A (ovaries/placenta protein)
*anomalies associated w/ preterm, IUGR, preeclampsia, fetal loss
nunchal transluscency
- 1st trimester screening (10.5-13.5 wk)
- looking for free hCG/PAPP-A levels
- combined w/ fld. collection from fetus neck
- screening test- NOT diagnostic
elevated AFP d/t…
- **open neural tube defect
- mutifetal gestation
- abd. wall defect
- renal anomalies
- maternal IDDM
low AFP d/t…
- overestimation of GA
- trisomy 21
- hydatiform mole
what happens if MSAFP abnormal
- lots of false neg. so need further/other testing
* further testing w/ specialized U/S, genetic specialists, etc
amniocentesis
•needle inserted into uterus and amniotic fld. withdrawn •used if -maternal age > 35 -family/past hx of genetic disorder -abnormal AFP/EDC -PG after 3+ SAb *done after 14 wk
risks w/ amniocentesis
- ROM, labor, miscarriage
- fetal cord injury
- infection
- abruption
- fetal death (rare)
- Rh isoimmunization
- amniotic fld. embolism
what amniocentesis detects
- fetal karyotype
- fetal AFP or AChE
- fetal Rh sensitization
3rd trimester amniocentesis
- assess fetal lung maturity if delivery considered before 38 wks
- diagnose fetal hemolytic dz d/t maternal Rh sensitization
fetal lung maturity
- L/S 2:1 (3:1 in diabetic mom) AND PG positive = mature
* PG neg = RDS
diagnosing fetal hemolytic dz
- done if mom antibody 1:8 or more
* high levels of bili in amnio fld. if positive
RN consideration amniocentesis
•supine w/ hip wedge •bladder EMPTY •monitor fetal status ***Rhogam after if needed •karyotype takes weeks •educate s/sx of infection/bleeding •encourage fld intake
chronic villus sampling
- 1st tri alternative to amniocentesis
- genetic testing @ 10-12 wks (earliest)
- sample from fetal placenta
- higher risk than amnio (limb defect)
- need FULL bladder
- Rhogam post procedure if Rh-
- transabdominal or transvaginal
Percutaneous umbilical blood sampling (PUBS)
•collecting fetal blood by fetoscope via umbilical vein under U/S guidance
*normally have to do in OR b/c often have to get baby out ASAP
indications for PUBS
- blood/chromosomal disorders
* evaluate isoimmune fetal hemolytic anemia/need for transfusion
Cordocentesis (blood studies)
- PUBS method
- Kleihaur Betke test- ensures blood from fetus
- CBC
- IC for Rh
- blood gases
- karyotyping
PUBS risks
- preterm labor
- amnionitis
- cord laceration
third trimester testing
- goal to evaluate whether intrauterine environment is supportive to fetus
- if not, deliver baby ASAP
nonstress test (NST)
•primary means of EFM fetal surveillance if increased risk of UPI •used if -IDDM mom -PIH -IUGR -previous stillbirth -post term -dec. fetal movement *report as reactive or non-reactive
healthy fetus w/ intact CNS will have…
- accels w/ movement
* indicates CNS fxn
reason for NST false non-reactive
- fetal immaturity
- sleep cycles
- medications
- chronic smoking
Reactive (normal) NST
•normal FHR w/ avg. variability
•> 32 wk- at least 2 FHR acc. of 15 bpm lasting 15 sec w/in 20 min
•28-32 wk- at least 2 FHR acc of 10 bpm lasting 10 sec w/in 20 min
*may have to wake baby w/ vibroaccoustic stim
Non-reactive (abnormal) NST
•doesn’t meet FHR acc. criteria in 2 attempts (40 min)
•requires further testing in L&D
-CST or BPP
•may have to induce
contraction stress test (CST)
•assesses FHR response to stress •requires EFM and induction of ctx -pitocin -nipple stimulation •more accurate than NST *invasive
negative (normal) CST
•no late decelerations
•minimum of 3 tx for 40-60 sec duration over 10 min
*reassurance that fetus will likely survive labor and that labor will occur in 1 wk
positive (abnormal) CST
•late decels in 50% of > ctx
•indicates UPI
•requires induction/c-section (baby out ASAP)
*POSITIVE=PROBLEMS
CST contraindications
•preterm •placental malplacement •multiple gestation •prior C/S w/ classic incision (vertical) -r/o uterine rupture
biophysical profile (BPP)
•U/S and EFM •accurate indicator of impending fetal death •5 parameters -FHR (NST) -fetal breathing movements -fetal tone -amniotic fld. vol. (AFV) *less invasive than CST
fetal hypoxia leads to…
•alteration in movement, breathing, HR
scoring of BPP
•0 OR 2 for each of the 4 parameters -FHR (NST) -fetal breathing movements -fetal tone -amniotic fld. vol. (AFV) •normal indicates CNS fxn and no hypoxia •abnormal and low fld. means labor needs to be induced
BPP numerical interpretations
- 8/8- normal BPP didn’t do NST
- 8/10- normal BPP and non-reactive NST
- 10/10-normal BPP and reactive NST
equivocal BPP
6
*repeat 24 hr
abnormal BPP
4 or less
*induce/c-section
amniotic fluid index (AFI)
- fluid pocket measurement
* detects polyhydramnios & oligohydramnios
polyhydramnios
•AFI > 25 •d/t -NTD -GI obstruction -twins -hydrops -DM *r/o PTL, ROM -> cord prolapse
oligohydramnios
•AFI < 5 •associated w/ ROM •r/o -renal abnormalities -IUGR -cord compression -deformity -hypoplastic lungs
doppler blood flow analysis
•see how well baby being perfused
fetal kick count instructions
•eat
•lay on side peacefully
*should feel 10 movements in 2 hrs
*no move w/in 12 hrs warrants further testing
