1 3rd trimester labs, 2 advance antenatal testing

Question 1

amniocentesis

1. gestational age to use
2. goals
3. risk of fetal loss

Answer 1

take fluid within the amniotic sac, look for baby’s cells floating in there to do DNA testing

1. >16 weeks
2. AFP, Genetic material. Can also determine L/S ratio
3. 1/200

Question 2

If mom is Rh-, do what test before deciding to give Rhogam?

Answer 2

Test for Rh-IgG Ab

If (+), then it’s too late.

If (-) AND dad is Rh+/unknown, give Rhogam to protect mom.

Question 3

Advanced antenatal testing procedures:

list the 5, from least to most dangerous to fetus

Answer 3

1. U/S
2. TCD transcranial doppler
3. amniocentesis
4. CVS chorionic villous sampling
5. PUBS percutaneous umbilical blood sampling

Question 4

Rhogam–when to give?

Answer 4

28 weeks, and delivery

Question 5

Antenatal Ultrasound:

1. gestational age limit?
2. goals (3)
3. risk of loss?

Answer 5

1. Any age
2. 1) intrauterine pregnancy
   2) fetal age
   3) fetal well-being
3. no risk of loss

Question 6

CVS

1. gestational age to use
2. goals
3. risk of fetal loss
4. Which moms to do this with?

Answer 6

Catheter sucks out tissues for sampling. invasive.

1. 6-12 weeks
2. genetics, karyotyping
3. 1/150
4. Moms with advanced maternal age (>35), and moms with prior hx of infants with birth defects, fetal demise, mental retardation

Question 7

What is Quad screen?

Answer 7

1. AFG
2. Estrogen
3. HCG
4. Inhibin

Question 8

Anemia: Third trimester screening

What do you expect to see on labs if there is anemia?

Answer 8

1. H/H: <10/30
2. low MCV

If both of the above, you can do Ferritin to confirm Fe deficiency. (low ferritin) No need to get bone marrow bx if these tests are all met.

Question 9

Gestational diabetes: how to screen? what values?

Answer 9

Must be after 20 weeks

1. 1-GTT (screening)

nonfasting 50g glucose, check 1 hour later. If >140, positive. Do 3-GTT

2. 3-GTT (confirm). Do fasting glucose test and then 100g glucose. positive if 2 of the following:

fasting >95

1 hr >180

2 hr >155

3 hr>140

(however, if fasting >125, that is good enough–no need to continue with 3-GTT)

If positive for GDM, treat with insulin

Question 10

Transcranial Doppler

1. gestational age to use
2. goals
3. risk of fetal loss

Answer 10

1. >20 weeks
2. screen for fetal anemia (if anemia, you can measure increase in flow in the cranium)
3. no risk

Question 11

Anemia: what happens during pregnancy?

What weeks is the nadir of Hb concentration?

Answer 11

Both plasma and Hb increase, but Plasma increases more.

So, although there is relative decrease in Hb concentration, there is increased total Hb so there is increased O2 carrying capacity and a reserve of RBCs

Nadir: 28-30 weeks. Hb should never go below 10.

Question 12

how accurate is U/S in determining fetal age?

Answer 12

Less precise later in pregnancy:

1st trimester +/- 1 week

2nd: +/- 2 weeks
3rd: +/- 3 weeks

Question 13

PUBS percutaenous umbilical cord sampling

1. gestational age to use
2. goals
3. risk of fetal loss

Answer 13

You can transfuse blood to the fetus. Do this only if fetus must be transfused for it to survice.

1. >20 weeks
2. confirm fetal anemia (after Transcranial doppler test), treat it
3. 1/30 (dangerous!!)