WK5D: Normal Diagnostic Laboratory Findings and Deviation

Diagnostic Laboratory Findings

pregnancy tests today are commercially available and can be performed by the trained personnel that are highly accurate and precise, if done with the correct technique.

Pregnancy testing

relies on the detection of an antibody to the hormone human chorionic gonadotropin (hCG) or a subunit in the urine or serum

Human Chorionic Gonadotropin

the first placental hormone produced and can be found shortly after implantation

Specimens:

1. Urine Blood

2. Progesterone Withdrawal Test

3. Ultrasound Imaging

Urine

test to yield accurate results and it should be done 10 to 14 days after the missed menstrual period. This period guarantee level of hCG and prevents false negative results.

Gravindex and Pregnosticon

are immunologic pregnancy test and approximately 95% accurate in diagnosing pregnancy and 98% accurate in determining the absence of pregnancy

Radioimmunoassay

tests for the beta subunit of hCG and considered to be so accurate as to be diagnostic for pregnancy

Urine Tests: Guidelines

• Collect first voided urine using clean, dry bottle free of detergent or contamination.

• Do not drink fluids from 8pm the night before to concentrate the urine

• Refrain from taking any drug 24 hrs. before the test

• Label the specimen with the woman’s name, date, and time of voiding.

• Bring the specimen to the laboratory immediately

• Refrigerate urine specimen-if more than one hour is pass before the specimen gets to the laboratory because room temperature is high enough to destroy hCG

Blood

with sensitive assays hCG can be detected in maternal blood at 7 days after conception and are accurate close to 100% of the time.

Progesterone Withdrawal test

a contraceptive pill is taken OD or TID (3xdays)

Progesterone Withdrawal test = woman is not pregnant.

If menstruation occurs within 10-15 days, the woman is not pregnant.

Progesterone Withdrawal test = woman is pregnant.

If corpus luteum produces enough hormones to neutralize the effect of withdrawn synthetic progesterone and no bleeding occurs, the woman is pregnant

Ultrasound imaging – (Ultrasound scanning or Scanning)

involves exposing a part of the body to high frequency sound waves to produce pictures of the inside of the body

Abdominal or Transabdominal

with the woman in supine position, the sonographer/radiologist applies the transducer on the lower abdomen

Vaginal or transvaginal

with the woman in lithotomy position, the sonographer/radiologist inserts into the vagina 2-3 inches of the vaginal transducer’s end with the protective cover and lubricating gel

Purpose

1. Diagnose pregnancy as early as 6 wks. Gestation.

2. Confirm the size, location of the placenta and amniotic fluid.

3. Discover complications of pregnancy.

4. Establish if fetus is growing and no congenital anomalies.

5. Predict maturity by measurement of biparietal diameter of the head

Types of Pelvic Ultrasound

• Abdominal or Transabdominal

• Vaginal or transvaginal

Biparietal diameter

• used to predict fetal maturity.

  • a. Measurement of fetal head (8.5 cm. or greater)

  • b. Weight. 2500 g (5.5 lb.)

Doppler Umbilical Velocimetry

measures the velocity at which RBC in the uterine and fetal vessels to assess blood flow

Placental grading for maturity

graded based on the amount of calcium deposits present in the base of the placenta

Placental grading for maturity

1. Grades 0: between 12 and 24 wks.

2. Grade 1: 30 – 32 wks.

3. Grade 2: 36 wks.

4. Grade 3: 38 wks. – suggest fetus is mature

Amniotic fluid volume

the amount of amniotic fluid present estimate fetal health

Hydramnios

20-24 cm

Oligohydramnios

< 5-6 cm

Nuchal translucency

described the appearance of a collection of fluid under the skin behind fetal neck

Magnetic resonance Imaging (MRI)

can identify structural anomalies or soft tissue disorder

Lateral Pelvimetry

in suspected cephalopelvic disproportion (CPD) with a danger sign of absence of lightening in a primigravida in active labor

Indications for lateral Pelvimetry

• Suspected CPD

• Previous difficult delivery

• History of severe vitamin D and calcium deficiency in childhood

• History of pelvic or spine injury

• Cases of severe scoliosis

LABORATORY ASSESSMENT

• Urinalysis – tested for proteinuria, glycosuria, nitrates, pyuria

• Complete blood count

• Genetic screen (G6PD glucose6phosphate dehydrogenase)

• VDRL serologic test for syphilis

• Blood typing (Rh factor)

• Maternal serum a-fetoprotein – done between 16-18 wks. of pregnancy

• Combs test – determination of whether Rh antibodies are present in an Rh (-) woman

• HIV screening

• Serum antibody titers for rubella, hepatitis, varicella

• Blood Serum Studies

• Tuberculosis Screening (Mantoux Test)

Fetal Biophysical Profile

• Is a noninvasive method of assessing the general well being of the fetus and the fetal assessment.

• BPP may be used as early as 26-28 weeks for the surveillance of high risk pregnancy.

• The test requires the use of an ultrasound and the electronic fetal monitor and the observation time takes about 30 minutes

Indications of Fetal Biophysical Profile

• Mother with gestational hypertension

• Fetus appears to be small or not growing properly

• Fetus is less active than normal (movement)

• Too much or too little amniotic fluid

Five Parameters of Fetal Biophysical Profile

• Fetal reactivity

• Fetal breathing movements

• Fetal body movements

• Fetal tone

• Amniotic fluid volume

Results of Fetal Biophysical Profile

• 8 - 10 fetus is considered to be doing well

• 6 - is considered suspicious

• 4 - denotes a fetus probably in jeopardy

Biophysical Profile Scoring

• Fetal breathing

• Fetal movement

• Fetal tone

• Fetal heart reactivity

• Amniotic fluid volume

Fetal breathing

at least one episode of 30secs. of sustained breathing movement w/in 30mins

Fetal movement

at least 3 episodes of fetal limb or trunk movement w/in 30mins.

Fetal tone

Observation must extend and then flex extremities or spine at least once in 30 mins.

Fetal heart reactivity

2 or more heart accelerations at least 15 beats/min

Amniotic fluid volume

A range of amniotic fluid between 5 and 25 cm must be present

Fetal heart sounds

• 10 – 11 wks. – ultrasound

• 10 wks. – Doppler

Daily fetal Movement Count (Kicks Count)

• 18 – 20 wks. – quickening felt by the mother

• 28 – 38 wks. – 10 x / hr. peaks in intensity

Rhythm Strip testing

• use for assessment of the fetal heart rate

  • Average FHR – 130 beats/ min.

  • Average fetal moves – twice every 10 mins. - causes heart rate to increase

Vibroacoustic Stimulation

• for acoustic (sound) stimulation

• Acoustic stimulator applied to the mother’s abdomen to produce sharp sound (80 db.), startling and waking the fetus

AFP/Triple Screen = High in the maternal serum (MSAFP)

fetus has an open spinal or abdominal defect.

AFP/Triple Screen = low estriol, elevated HCG, and low AFP

often associated with Trisomy 21 (Down syndrome).

Amniocentesis

• Amnion for sac and kentesis for puncture. Scheduled between the 14th and 16th week

• removal of fluid from the amniotic cavity by needle puncture. An ultrasound is performed first to determine the safe site where the needle can be inserted.

• During the procedure, the fetus is continuously monitored by ultrasound to ensure its wellbeing.

Complications OF Amniocentesis

hemorrhage from the penetration of the placenta, infection of the amniotic fluid and puncture of the fetus

Purposes of Amniotic Fluid Analysis

• Detection of fetal abnormalities early in pregnancy

• To determine fetal lung maturity

• Lecithin/Sphingomyelin ratio

• Lung Profile

• Amniotic Fluid Bilirubin

• Rh incompatibility

• For detection of certain infections

• Detection of fetal abnormalities early in pregnancy

Nursing Care during Amniocentesis

• Assist client to empty her bladder before the procedure

• Place in supine position and drape properly

• Put rolled towel under right hip to tip body to the left and remove pressure of uterus on vena cava

• Instruct not to take a deep breath and hold it while the needle is being inserted as it will shift the uterus and needle may hit placenta or fetus

• Inform the patient that it is not painful because anesthesia will be applied at the insertion site. She may experience pressure sensation during the insertion of the needle.

• Monitor (fetal heart tones) FHT before, during and in 30 minutes after the test.

Instruct patient to observe for

• Infection

• Uterine cramping

• Vaginal bleeding

Reportable s/sx of Chorionic Villi Sampling

• Chills or fever (infection)

• Uterine contraction or vaginal bleeding (threatened miscarriage)

Chorionic Villi Sampling

• Is a transcervical or transabdominal insertion of a needle into the fetal portion of the placenta, at the area of the chorion frondosum

• CVS is performed at 8-12 weeks gestation under ultrasound guidance to ensure that the fetus is unharmed.

Purpose of Chorionic Villi Sampling

Chorionic villi cells are examined to detect chromosome abnormalities such as Down syndrome and genetic disorders such as cystic fibrosis

biopsy & analysis of chorionic villi

• for chromosomal analysis done at 8 to 10 weeks of pregnancy chorion cells are located by ultrasound

• A thin catheter is inserted vaginally or needle biopsy is inserted intravaginally or inserted abdominally, and a number of chorionic cells are removed chromosone analysis (genetic defect)

Chorionic Villi Sampling Facts

• Instruct client to report bleeding, infection or leakage of fluid after procedure

• Some instances of limb reduction syndrome

• Less than 1% risk leading to excessive bleeding, or pregnancy loss

AFP/Triple Screen

• This test involves measurement of Alpha fetoprotein (AFP), estriol and HCG in maternal serum at 15-20 weeks of gestation to screen for fetal structural & chromosomal abnormalities.

• Alpha-feto protein is a substance produced by the liver that is present in amniotic fluid and maternal serum.

• Estriol is initially tested. If the result is abnormal, the woman is next referred for ultrasound to confirm gestational age and to evaluate for neural tube defects (NTD) and other structural abnormalities.

NST = adequate oxygenation and intact CNS

accelerations of FHR with fetal movement

reactive NST

The baby’s heart rate should accelerate, by 15 beats for at least 15 seconds, twice in a twenty minute period. This is a good sign that the fetus is healthy. A reactive NST indicates intrauterine survival for one week.

Non- Stress Test (NST)

An assessment of fetal well-being that analyses the response of the fetal heart to fetal movement

NST is nonreactive

The doctor may order a CST. The usual preparation is to feed the mother with food or fluids before the test to stimulate fetal movements

Positive Result of CST

there is persistent late decelerations w/ more than half the contractions; maybe associated w/ minimal or absent variability. A positive CST means that the fetus is no longer receiving adequate oxygen and needs to be delivered.

Negative Result of CST

There is no late deceleration in a 10-minute period and this means that it is safe for the fetus to remain in utero for the next 7 days

Contraction Stress Test (CST)

• Assess the ability of the fetus to withstand the stress of uterine contraction done during labor

• evaluating the respiratory function of the placenta.

• Testing is initiated when 3 contractions in every 10 minutes are attained. The test takes about 60-90 minutes to perform.

Induced or spontaneous contraction

decrease transport of O2 to the fetus. A healthy fetus maintains a steady heart rate.

placental reserve is insufficient

fetal hypoxia and decrease in FHR occur.

Periodic Changes

1. Accelerations

2. Early Decelerations

3. Late Decelerations

4. Variable Decelerations

Early Decelerations

• periodic decreases in FHR resulting from pressure of the fetal head during contractions.

• Beginning when the contractions begins and ending when the contractions end (mirror image)

• Normal – late in labor

Late Decelerations

delayed decelerations until 30 to 40 seconds after the onset of a contraction and continue beyond the end of the contraction

Variable Decelerations

Decelerations that occur at unpredictable times in relations to contractions.

Accelerations

temporary normal increases in FHR caused by fetal movement or compression of the umbilical vein during contraction

Cord prolapsed

Indicate compression of cord = Variable Decelerations

Position in Variable Decelerations

lateral or T-position