L3 Prenatal Screening and diagnostic test

Suggest the benefit of prenatal screening. (7)

1. Detection of potential genetic or chromosomal abnormalities at an early stage

2. Couples can decide on further diagnostic test in early pregnancy

3. Enable early intervention and proactive care

4. Reduce anxiety and uncertainty

5. Allow couples to prepare emotionally, gather information about their pregnancy and future care for their child

6. Facilitate informed decision-making

7. Provide an opportunity for family planning, e.g.

   • The option of genetic counseling

   • Exploring reproductive technologies

   • Plan for future pregnancies based on the risk factors identified

List the high risk group for prenatal diagnostic testing (9)

• Maternal age ≥35

• Obesity (pre-pregnancy BMI >30)

• Aboriginal, African, Asian, Hispanic, South Asian ethnicity

• Family history of genetic disorders / DM

• Maternal health problems:

  • Hypertension, epilepsy, thyroid disease, heart, blood disorder

• Previous pregnancy with gestational DM

• Previous delivery of a baby large than 4000gm

• Corticosteroid use during pregnancy

• Multiple pregnancy

Suggest a test that will be do in every antenatal visit

Urinalysis for protein & glucose

Why HCG level drop gradually after the peak level at week 8 ?

• HCG function is to prompts the corpus luteum to continue secrete estrogen & progesterone in order to maintain the uterine lining thickness

• After week 8, the placenta is mature to take over the production of progesterone from corpus luteum

Suggest a prenatal screening that can act as an indicator of fetal life.

• Fetal movement count (Kick count)

What is the normal & abnormal findings of fetal movement count ?

Normal: women counts 10 distinct kicks of her fetus per 1-2 hours

Abnormal: No fetal movement for 12 hours —> notify nurse / doctor

Suggest a prenatal screening that can use to monitor the fetal heartbeat and uterine activity over time

• Cardiotocogram

Suggest a prenatal screening for fetal surveillance before the onset of labour

• Nonstress test (NST)

  • (a form of cardiotocography (CTG))

How to interpret the result of Nonstress test (NST)

• Reactive NST: ≥2 FHR accelerations within 20 mins period

• Non-reactive NST: ≤2 FHR accelerations during a 40 mins period

• Variable decelerations NST

  • No recurrent 經常性的 and < 30s → no further investigation

  • Recurrent: ≥ 3 episodes in 20 mins → extend monitoring

  • Persist for ≥ 1 minute → immediate attention

List the types of prenatal screening / diagnostic test to be performed in 1st trimester (3)

1. Ultrasound

2. Chorionic villus sampling

3. Maternal serum blood test / Multiple marker screening

List the types of prenatal screening / diagnostic test to be performed in 2nd trimester (6)

1. Ultrasound

2. Amniocentesis

3. Percutaneous umbilical blood sampling (PUBS) / Cordocentesis

4. Maternal serum blood test / Multiple marker screening: Triple screening / Quadruple screening

5. Glucose screening

6. Magnetic Resonance Imaging (MRI)

List the types of prenatal screening / diagnostic test to be performed in 3rd trimester (2)

1. Ultrasound

2. Group B streptococcus prenatal screening

How to prepare patient for transabdominal / transvaginal ultrasound respectively

Transabdominal:

• Tell the woman to drink lots of water to allow full bladder anatomically push the uterus up to the abdomen

Transvaginal:

• Tell the woman to empty the bladder

What are the purpose of ultrasound assessment in 1st trimester (1-13 weeks) ? (6)

1. To check the embryo is developing inside the uterus

2. Confirm the number of embryos

3. Calculate the gestational age and the expected date of delivery

4. Determine the foetal age and growth

5. Guide doctors for other diagnostic test, e.g. chorionic villus sampling

6. Identify soft ultrasound markers: check the neck areas, aka Fetal nuchal translucency screening

   1. Perform at ~11-13 weeks

   2. examine the area at the back of the foetal neck for increased fluid or thickening

   3. Extra tests should be performed when the nuchal translucency more than 3.5mm

What are the purpose of ultrasound assessment in 2nd trimester (14-26 weeks) ? (4)

1. Evaluate the foetus from head to toe for any developmental issues

2. Determine size, position and engagement of the foetus 

3. Quantify amniotic fluid amount

4. Check the foetus's sex according to the parents' desire

What are the purpose of ultrasound assessment in 3rd trimester (27-40 weeks) ? (3)

(Usually perform it after 30 weeks)

1. Continue to monitor the baby’s growth

2. Identify the location of the placenta

   • If total placenta (completely cover the os) —> might have many blood lose during delivery

3. Identify the position and presentation of the foetus

   • Anterior (head at the os) / Vertex / Cephalic presentation —> natural passage

   • Breech Transverse lie —> recommend C-section

What is the indication of chorionic villus sampling ? 

History of or suspicion of a genetic disease, chromosomal abnormalities or metabolic disorders

Suggest an advantage of chorionic villus sampling

the results are available much earlier than amniocentesis

What is the purpose of chorionic villus sampling ? 

To detect fetal genetic and chromosomal abnormality, perform at ~ 10-13 weeks

What are the risk of chorionic villus sampling ? (6)

·      Abdominal cramping

·      Bleeding

·      Leaking of amniotic fluid

·      Infection

·      Miscarriage

·      Preterm labour

What is purpose of amniocentesis ?

To diagnose certain chromosomal conditions, e.g.

Þ   Down syndrome

Þ   Neural tube defects

Þ   Cystic fibrosis

List the nursing intervention of amniocentesis (pre-pocedure) (5)

Invasive procedure !!!

1. Educate the client to monitor that there will be red discharge in the first 2 days, then should transit to brown and then resolves

2. Uterine cramping that usually happened immediately after the procedure

3. Amniocentesis: a small amount of leaking of amniotic fluid may be noted on the first day

4. Advice resting for 24 hours

5. Avoid exercise, heavy lifting and sexual intercourse for several days

What is the purpose of percutaneous umbilical blood sampling (PUBS) / cordocentesis ?

Obtain a sample of blood from the foetal umbilical cord after 20 weeks of gestation:

1. To detect blood disorders

2. To deliver medication or blood transfusion to a fetus

What types of blood markers will be examinated in the 1st trimester ?

PAPP-A = Pregnancy-associated plasma protein A

hCG = Human chorionic gonadotropin

cfDNA = Cell free DNA, the fetal DNA circulate in mother’s circulation

What types of blood markers will be examinated in the 2nd trimester ?

• hCG

• AFP = Alpha-fetoprotein

• E3 = Oestriol

• Inhibin-A (Max. at 36 weeks)

Triple or Quadruple screening

If PAPP-A level drop, what might be the suspected findings ?

PAPP-A = Pregnancy-associated plasma protein A

·      A lower birth weight baby

·      Perterm birth

·      Preeclampsia

·      Mid trimester miscarriage

·    Increased risk of chromosomal abnormality

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PAPP-A is produced by the syncytiotrophoblast cells of the placenta. PAPP-A helps in the breakdown of insulin-like growth factor-binding proteins (IGFBPs), which control the availability of IGF to cells for growth and development.

If hCG level increase, what might be the suspected findings ?

• Multiple pregnancy

• Hydatidiform mole 葡萄胎

• Down syndrome (Trisomy 21) [2nd trimester]

If hCG level decrease, what might be the suspected findings ?

·      Fetal death / still birth [1st, 2nd trimester]

·      Trisomy 18 [2nd trimester]

·    Ectopic pregnancy

·      Incomplete miscarriage

·    Threatened spontaneous abortion

If AFP level increase, what might be the suspected findings ?

AFP = Alpha-fetoprotein

·      Open neural tube defects, such as spina bifida

·       Twins / multiple pregnant

·     Stillbirth 死胎

If AFP level decrease, what might be the suspected findings ?

AFP = Alpha-fetoprotein

·      Down syndrome (Trisomy 21)

·    Trisomy 18

If E3 level drop, what might be the suspected findings ?

·      Down syndrome (Trisomy 21)

·      Trisomy 18

·    Stillbirth 死胎

Inhibin-A findings in serum blood test might indicate what kind of suspected findings ?

·      Down syndrome

·      Preeclampsia

·      GDM

·    Macrosomia巨大兒

Describe the blood result in 2nd trimester if suspected of neural tube defect.

• AFP increase

• uE3 normal

• hCG normal

Describe the blood result in 2nd trimester if suspected of trisomy 21 (Down syndrome).

• AFP decrease

• uE3 decrease

• hCG increase

Describe the blood result in 2nd trimester if suspected of trisomy 18.

• AFP decrease

• uE3 decrease

• hCG decrease

Describe the blood result in 2nd trimester if suspected of multiple pregnant.

• AFP increase

• uE3 normal

• hCG increase

Describe the blood result in 2nd trimester if suspected of still birth.

• AFP increase

• uE3 decrease

• hCG decrease

What is the purpose / indication of Magnetic resonance imaging (MRI)

• Do when the baby suspect of hydrocephalus

• Combined with USG at or after 18 weeks of gestation

What are the indication of checking cfDNA markers in the 1st trimester (4)

1.     Higher risk for a foetal chromosome disorders

2.     Maternal age ≥ 35

3.     Previous child with a chromosome disorders

4.     Abnormal results on an ultrasound or other prenatal test

cfDNA findings in serum blood test might indicate what kind of suspected findings ?

·      Down syndrome

·      Trisomy 18

·    Trisomy 13

Describe when and how to do group B streptococcus prenatal screening ?

Þ   Perform between 35-37 weeks of gestation

Þ   Taking both low vaginal & rectal swabs