Chapter 9: Assessing the Fetus

What is the primary objective of prenatal screening and diagnosis?

To detect genetic disorders and/or abnormalities that could affect the woman, the fetus, and the newborn.

Screening

Detects and identifies individuals who are at RISK for abnormalities or diseases. Detects congenital abnormalities

What procedures do we use to screen? (5)

Drawing blood

First trimester screening

Triple screen

Quadruplet screen

Cell free DNA screen

What is considered a combined single screening test?

A Integrated and sequential screening

What is one limitation of using a single screening test?

Risk for false-negative and false-positive result

Diagnostic

Most precise test for a given condition performed after a screen test in order to provide a diagnostic

what are the 3 diagnostic procedures?

Chorionic Villius sampling

Amniocentesis

preimplantation genetic diagnosis

Ultrasound

High frequency sound waves that obtain real time images of maternal structures, placenta, amniotic fluid, and fetus during the 3 trimesters. Also used with diagnostic testing

What kind of ultrasounds are there?

2D, 3D, 4D

2D ultrasound

An ultrasound where sound waves bounce off organs/fluids. Flat picture of image

3D ultrasound

An ultrasound that can get height, width, depth of structure, can identify abnormalities

4D ultrasound

An ultrasound that can stream live video images

Non-medical ultrasound

An ultrasound that isnt necessary

which ultrasound is primarily for gender identification

3D and 4D ultrasound

What routes can an ultrasound be given?

Transabdominally and Transvaginally

what requirement should be done in the first trimester to receive a ultrasound for best results?

The bladder must be full

what are the three categories of an ultrasound

Standard

Limited

Specialized

Standard Ultrasound

An ultrasound that is 2D, Looks at anatomy, biometry, fetus, cardiac activity

limited ultrasound

An ultrasound that Looks for a specific problem or concern that requires further evaluation

Specialized Ultrasound

An ultrasound that looks at a specific structure of organ system

First trimester ultrasound

An ultrasound that confirms date/gestational age, # of fetuses, abnormalities, and location of fetus.

What weeks can an embryo be seen in an ultrasound

5-6 weeks after LMP

Where is the ultrasound placed during the first trimester?

Placed in lithomy position, transvaginally, takes about 10-15 mins

Where is the ultrasound placed during the second or third trimester?

Transabdominally because uterus is out of pelvis

Seond/third trimester ultrasound

Ultrasound that confirms viability, anatomy, gestational age, placental location, fetal presentation, biophysical poifle, fetal growth, amniotic fluid

Gestation age is less accurate when?

After 1 trimester.

what are 2 ways to determine gestational age?

1. Calculating fetus head, abdomen, and length measurements

2. 3 Ultrasounds taken 2 weeks apart and compare to standard.

What is the procedure of a second/third trimester ultrasound?

Supine on bed/table

Head and knees supported

Warm transmission gel

Wedge on either side of hip to provide comfort

What does a 1st trimester screening screen for?

Trisomy 21 and trisomy 18

Nuchal translucency screening (1st trimester)

a special ultrasound test of the fetus to screen for the risk of Down Syndrome and other birth defects. Fluid-filled space measured at the back of the fetal neck

hCG (human chorionic gonadotropin)

pregnancy hormone, produced by embyro, peaks at 8-10 weeks

Nasal bone assessment

An assessment that detects trisomy 21.

Midace hypoplasia and flattered nose

11 to 14 weeks

When is cell free fetal DNA found?

In maternal serum 5-7 weeks

What does cell free fetal DNA target

Trisomy 21, 18, 13, and sex chromosomes

What is the limitation of cell free fetal dna?

Cant distinguish between fetal and maternal DNA

Who was cell free fetal dna designed for?

High Risk Patients

multiple marker screening

Screen during 2nd/3rd trimester that resports womans risk for triosomy 21, 18, and open NTDs.

When can you do a multiple marker screening?

15-22 weeks

chorionic villus sampling (CVS)

A technique for diagnosing genetic and congenital defects in a fetus by removing and analyzing a sample of the fetal portion of the placenta.

When is a CVS done and how can it be done?

10-12 weeks, transcervical or transabdominally

Who is CVS done for?

people with KNOWN fetal abnormalities on ultrasound or with history of chromosome abnormalities

Amniocentesis

A technique of prenatal diagnosis in which amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus.

What else does an amniocentesis determine?

fetal lung maturity

when can amniocentesis be done?

15-20 weeks

what is a concern with amniocentesis?

Pregnancy loss

When does results of an amniocentesis occur?

10-14 days

when is a precutaneous umbilical blood sampling performed?

after 18 weeks

Precutaneous Umbilical Blood Sampling

Aspiration of fetal blood from the umbilical cord.

What does a PUBS assess for?

Fetal Anemia, can give transfusion via cord based on hematocrit

Who Should Be Offered Prenatal Screening?

Women 35 years or older

Abnormal ultrasound findings

Diabetes

Hypertension

Obesity

Substance abuse

When is antepartum fetal surveillance initiated ?

24-32 weeks for high risk pregancies

Fetal movement counting

A fetal surveillance method that measures fetal well being and conservation of oxygen consumption

Count to 10 method

A method to determine fetal movement.

Rest in quiet location

Count kicks/rolls

Count to 10: 10 distinct movements in a 1 to 2 hour period =

nonhypoxic

what should you do if a woman cannot find movements due to obesity or any other circumstance?

Assist with abdominal palpation

When does fetal movement peak?

9pm-1am because a fall of glucose level

Nonstress test (NST)

An antepartum evaluation of fetal well being performed during the third trimester. A noninvasive test that monitors the FHRto fetal movement. Risk for uteroplacental insufficiency

What is the procedure of NST?

Semifowlers

Transducer applied to abdomen

Let fetus be exposed to sound

Let patient have an empty bladder

Why do we want the patient to be in semi fowlers position during NST

Reduce the risk for aortocaval compression

Reactive/Reassuring NST interpretation

2 or more FHR accelerations 15 beats x 15 seconds within 20 mins

Nonreactive/nonrecurring NST interpretation

Less than 2 accelerations within 40 mins

Deceleration that persists for 1 mins or longer =

C-section or still birth

What to do if continuously see deceleration?

Monitor for extended period

Contraction stress test

.a stress test used to evaluate the ability of the fetus to tolerate the stress of labor and delivery. Uses oxytocin or nipple stimulation

Abnormal CST

Late decelerations, hypoxemia

Negative CST results

No late decels

Postive CST result

Late decels, min of 50% of contractions

Equivocal-suspicious CST

Intermittent or variable late decels

equivocal CST result

Decels with contractions that are every 2 mins, last longer than 90 seconds

unsatisfactory CST

Fewer than 3 contractions in 10 mins or tracing could not be determined

Biophysical Profile (BPP)

Method for evaluating fetal status during the antepartum period based on five variables originating with the fetus: fetal heart rate, breathing movements, gross body movements, muscle tone, and amniotic fluid volume.

Short term markers: BBP

FHR, breathing, movement, tone

Long term: BBP

Amniotic fluid amount

when does fetal tone develop?

7 to 8 weeks

When does fetal movement begin

9 weeks

when does breathing begin?

10 weeks, more apparent 19-20 weeks

Amniotic fluid production begins?

10 weeks

How is BBP evaluated?

each area is scored as a 2, which is normal or a 0 for abnormal

what is a perfect BBP score

8 to 10