Prenatal & Diagnostic Tests

1. to detect congenital abnormalities
2. evaluate fetal status
3. medical conditions in mother (DM, HTN, STDs)
4. demographic factors (age<16 or > 35, inadequate PNC, poverty)

1. HX of LBW infant (<2500g or <5lbs) or preterm
2. multifetal PG
3. malpresentation (breech)
4. previous fetal loss or infant w/congenital anomaly
5. previous infant >4000g or >8lbs
6. hydramnios (>2000ml @ term)
7. oligohydramnios (<500ml at term)
8. decrease or absence of fetal movement
9. uncertain gestational age (can get false results)
10. suspected IUGR
11. discordant fetal growth with twins (one larger than the other)
12. postmaturity (>42 wks)
13. preterm labor (>20wks & <38wks)
14. grand multigravida (>5 PGs)

usually done to identify if there is truly a pregnancy there.
*Transvaginal - uterus deep in pelvis at this time; full bladder not needed.
**Procedure: lithotomy procedure, transvaginal probe (covered w/disposable cover & gel/lubricant used), 10-15 mins (very short & not painful)
NO KNOWN RISKS

*done to confirm fetal viability (growing properly? probs?)
*evaluate fetal anatomy (ID major systems & organ structures)
*Estimate fetal age (approx 18 wks get femur length, biparietal diameter, abd circum; after 32 wks get EGA via US, always 2 wks off)
*compare growth of fetuses in multiples
*evaluate amniotic fluid volume
*determine fetal presentation
*guide needle placement for amnio/PUBS
*check placenta position (previa)

*full bladder required in 2nd trimester only
*maternal position: HOB elevated, slightly turned to side (L or R) w/wedge, avoid hypotension from pressure on abd aorta
*Transmissin gel
*Transducer moved over abdomen
*takes 10-30 mins

noninvasive
immediate results
portable machines
clear visualization of fetal structures

can't ID genetic abnorms
expensive (insurance will pay for 1-2, more if medically needed)

*assess blood flow thru the umbilical artery
*detects/confirms IUGR
*assesses blood flow (maternal & fetal), 2 arteries & 1 vein; vein is larger & brings blood to baby, arteries take blood back to mom.
*Placental insufficiency (if severe, diastolic flow may be absent or reversed)
PROCEDURE: performed during US

*predominant protein in fetal plasma to fetal urine to amniotic fluid, some AFP crosses placenta.
*MSAFP (maternal serum AFP) & AFAFP (amniotic fluid AFP). Check mother's blood or amniotic fluid to find it.

concentrations vary with gestational age. Level will change as gestational age changes; gets less concentrated w/age.

*chromosomal trisomies
*Overestimation of gestational age (normal fetus)
*incorrect maternal weight (normal fetus) - AFP diffuses into a larger maternal compartment in a heavier woman.

*open neural tube defects (anencephaly, spina bifida)
*abdominal wall defects (gastroschisis, ompalocele)
*fetal blood in amniotic fluid (nicked baby)
*underestimation of age
*multifetal gestation
*less than true maternal weight (underweight)
*maternal IDDM

*screening, not diagnostic (further tests may lead to anxiety/decisions for parents)
*benign conditions (overestimation of EGA) can cause "abnormal" levels which leads to anxiety/expense for parents for no reason (do US 1st to estimate gest age)
*timing imposes limits on usefulness (16-18 wks)
*closed defects increase MSAFP so normal level doesn't guarantee fetus free of structural abnorms

*Offered 16-18 wks
*screening, not diagnostic
*informed consent required (b/c invasive), risks, potential probs
*if abnormal -> further testing=US, amnio

*simple
*least invasive & most economical way to screen for NTD
*prenatal DX allows time for parents to prepare

3 tests done together (Hcg + unconjugated estriol + MSAFP) to detect trisomies 18 & 21
*purpose is to increase the detection of trisomy 18 & 21

*blood draw 16-18 wks
*test + if:
>MSAFP = low
>Estriol = low
>hCG = high
*further testing needed if +; amnio, US, karyotyping (photomicrograph of a single cells chromosomes)

*Chorionic villi are projections from the chorion (outer membrane of amniotic sac) that burrow into endometrial tissue as the placenta is formed
*cells are fetal in origin - rapidly dividing
*reflect chromosomal and genetic make-up of fetus
PURPOSE: Dx of fetal chromosomal, metabolic, or DNA abnorms

*>35 yrs
*Hx of fetus w/anomalies
*carriers/couples who exhibit genetic defects
*ID Rh type of fetus at risk for maternal isoimmunization
**CVS only done in HIV+ pts if absolutely necessary

*Informed consent required
*10-12 wks gestation
*Transcervical (vaginal) or transabdominal (needle inserted & sample pulled).
**Transcervical is least invasive; need US present
POST-Procedure: check FHR, maternal VS, bleeding

*10-12 wks = earlier results than amnio
*allows choice for early abortion

*PG loss rate = 0.5-1%
*chance of increased limb reduction if done before 10 wks
*potential uterine infection
*Rh sensitization may occur if fetal RH+ blood cells enter the circulation of an RH- mother. Rhogam s/b administered to all unsensitized RH- women following procedure.
*labor intensive & costly

Transcervical contraindicated if the mother has an active cervical or vaginal infection (test mom before doing this approach)(could include herpes, gonorrhea, etc)

*aspiration of amniotic fluid
*Purpose: 2nd trimester
>ID chromosomal or metabolic abnorms (previous birth of infant w/chromosomal abnorm, NTD, body wall defect)
>AFP level
>evaluate fetal status w/Rh- sensitized mom
>maternal age >35
*Purpose: 3rd trimester
>fetal lung maturity (LS Ratio) for mom w/PIH, preeclampsia, DM
>Dx fetal hemolytic disease (Rh compatibility)
>fluid reduction w/polyhydramnios

*L/S is equal until about 30th week; lecithin continues to rise after 30th week.
*if >2:1 general indicative that surfactant is adequate and the fetal lungs are mature
*if mom has DM, L/S ratio is not always an indicator of lung maturity

*can tell if Rh- mom has been sensitized to Rh+ blood.
*mom's antibodies destroy fetal Rh+ blood cells
*fetal bilirubin content indicates level of destruction
*FETUS: erythroblastosis fetalis (blue babies; can transfuse the baby in utero) & hydrops fetalis

*informed consent required
*supine w/wedge (L or R)
*baseline VS & FHR (on monitor throughout procedure)
*US to ID largest pocket of fluid & guide needle insertion
*antiseptic (to clean) & local anesthetic to skin
*3-4", 20-21 gauge needle inserted
*20ml removed w/initial 2 ml discarded

*EFMx30-60 min to assess for contractions & FHR, V/S
*instruct pt to report persistent uterine contractions, vaginal bleeding, amniotic fluid leakage, or fever
*administer Rhogam to unsensitized Rh- mom (w/i 72 hrs of amnio)
*if mom is HIV+ only do amnio if absolutely necessary

*simple, relatively safe
*Dx of many fetal abnormalities
*determination of fetal lung maturity
*brief, relatively painless
*few complications
*fetal loss rate <1%

*timing in 2nd trimester r/t genetic prenatal Dx: amnio done at 15-20 wks; may take 2+ weeks for results.
*potential PTL (rare)

*evaluates the ability of the fetal heart to accelerate under no stress

*RN explains purpose of the NST (put you in bed, put monitor on you & listen to heartbeat)
*positions pt in semi-fowlers, side-lying or lateral tilt (using wedge
*apply external fetal monitoring equipment to detect fetal heart tones, UCs, and/or fetal movement
*Pt given an event marker to press each time she feels the baby move
*usually 20 mins long, may need 40 mins to allow for normal fetal sleep-wake cycles

**2 accels peaking at 15bpm above the baseline lasting 15 secs in 20 minute timeframe.

**2 accels peaking at 10bpm above the baseline lasting 10 seconds in 30 minutes

*tracing doesn't demonstrate the required accels w/i a 40 minute period (if no accels in 20 mins, do for 40 mins)
**May require further testing (CST-contraction stress test, Biophysical Profile (3D US)

*noninvasive
*no risk to mom/baby
*easy to administer
*may be repeated as often as necessary
*results available immediately

*fetal sleep can cause false positive (nonreactive) results - this can be corrected by giving mother OJ to raise glucose level, by manipulating the women's abdomen & by acoustic stimulation

*provide futher assessment of fetal well-being when an NST is nonreactive (positive).
*Record the response of the FHR to stress induced by UC's.
*UC's compress arteries & veins in the placenta causing decreased fetal O2 level
*if the fetus has adequate O2 then it can tolerate this temporary hypoxia.
*Decels seen if baby is hypoxic.

*explain procedure & purpose.
*semi-fowlers, side-lying or lateral tilt using wedge.
*external EFM applied to record both UCs & FHR
*must evaluate 3 UCs on minimum 40 secs each in a 10 minute period.
*Can take up to 2 hrs

nipple stimulation
IV infusion of low dose oxytocin

no late decels (good)

late decels follow 50% or more of the UCs, even if fewer than 3 UCs in 10 mins (bad)
**3 types
1. equivocal-suspicious
2. equivocal-hyperstimulation
3. unsatisfactory

intermittent late or significant variable decels

FHR decels occur in the presence of excessive UCs (more than q 2 mins or lasting longer than 90 secs)

fewer than 3 UCs within 10 mins or a tracing that cannot be interpreted

*few, availability of other tests that are more diagnostic of fetal well-being & placenta function has reduced its original advantages.
*allows f/u of a NR NST
*+CST allows MD to look at options and make plans for the birth of an infant who may be compromised b/c of decreased placental functioning before or during labor.

*cannot do if UCs contraindicated (preterm labor, PROM, prematurity (or high risk for prematurity), placenta previa)
*hyperstimulation may occur; late decels may be present that wouldn't normally occur w/UCs
*time-consuming
*tedious
*errors in interpretation
*must be done in hospital

1. NST
2. Fetal breathing
3. gross fetal movements
4. fetal tone
5. amniotic fluid volume

*late decels - 1st sign
*accels disappear - 2nd sign
*fetal breathing mvmt stops
*fetal movement ceases (late sign)
*fetal tone absent (fetus already compromised)

Fluid
*fetal hypoxia>fetus shunts blood from non-critical areas (kidneys, lungs) toward heart/brain>decreased blood flow decreases/ceases amniotic fluid production>oligohydramnios>indicates prolonged fetal hypoxia

*non-invasive
*outpatient
*results immediate
*allows conservative tx of high risk pts b/c delivery can be delayed if fetal well-being is demonstrated.

*additional research to refine interpretation
*variables given equal weight
*relationship of low BPP scores to long-term development isn't complete

Normal = 8-10 points
Equivocal = 6 points
Abnormal = 4 or less points

**Purpose: aspiration of fetal cord blood for DX/TX of intrauterine Rh disease, genetic studies, dx of abnormal clotting factors, severe IUGR, acid-base status of fetus.
**Procedure: puncture into cord; US to locate fetus, placenta & umbilical cord.
*Umbilical vein (brings blood to baby) is larger and less likely to constrict during the procedure.
*POST procedure: monitor bleeding via US, EFM to monitor FHR

fetal loss
infection
fetal bradycardia
cord laceration
cord hematoma
thrombosis
thromboembolism
premature labor
PROM

*movements by the fetus, as assessed by the mother
*associated with fetal condition

*same time daily
*2 most common protocols:
1. count fetal movements for 30 minutes TID. Notify MD for fewer than 4 mvmts in 30 mins
2. count fetal mvmts for 1 hr daily. if fewer than 10 continue counting for another hour. Notify MD for fewer than 10 in a 2 hr period.

noninvasive
inexpensive
convenient to mother

many variables can make a difference in the mvmts
(sleeping, mother's perception of mvmt, time of day, maternal use of drugs).