Antenatal care and Screening Flashcards
Organogenesis can initiate as early as how many weeks?
3-8 weeks
- important for pre-conception counselling as this often begins before people realize they are pregnant
What would you recommend wrt folic acid supplementation to a patient wishing to become pregnant?
- Folic acid supplementation 8-12 weeks preconception
- Continue until the end of T1 (week 14) to prevent NTD
- 0.4-1mg in all women
- 5mg if:
- previous NTD
- anticonvulsant use
- DM
- BMI > 35
When would you recommend a woman take 5mg of folic acid to prevent NTD?
1) Previous NTD (n other preg, or family hx)
- 10 fold increase in risk
2) Antiepileptic medications
- carbamazapine
- valproic acid
3) DM
- Increased risk
4) BMI > 35
- Increased risk
- uptodate doesn’t recommend using higher dose though?
5) Other (decreased absorption)
- Celiac disease
- Gastric bypass
- IBD
What infection screening is done in pregnancy? (6)
- Rubella (immunity)
- HBsAg
- hep B surface antigen (marker for previous infection)
- if positive baby should be vaccinated, as some patients develop chronic infection which can be passed
- VDRL
- Pap smear (if due)
- Gonorrhea/Chlamydia testing
- HIV
What is Naegles rule?
- Used to estimate date of delivery using LMP
- 1st day of LMP + 7 days - 3 months
- If cycle > 28d modify by adding number of days over 28
Your patient’s LMP was March 10th, using Naegles rule what would their EDD be? Assume 28d cycle
- December 17th
Which investigations would you order for a patient during their first prenatal visit?
- CBC
- Blood group and Rh status
- Rh antibody screen
- Infection screening as per preconception councelling
- Urine R & M, midstream urine for C&S
- Screen for proteinuria and bacteruria
- Urine or cervical gonorrhea and chlamydia PCR testing
- Pap if due
How frequently should a woman be seen for prenatal vists in uncomplicated pregnancy?
1) under 30 weeks
- every 4-6 weeks
2) 30 weeks to 36 weeks
- every 2-3 weeks
3) 36 weeks until delivery
- every 1-2 weeks
Describe what would be part of your pre-natal visits?
1) Estimate GA
2) History
- fetal movement
- BP
- Weight change
- SFH
- Leopolds maneuve in 3rd trimester
- position and presentation of fetus
- Urinalysis for glucosuria, proteinuria
- fetal heart rate starting at 10-12 weeks using doppler
What is leopolds maneuver? How is it performed? When do you start doing it?
1) physical exam to determine the position of the fetus in the uterus
2)
First:
- determine which fetal part is lying furthest from the pelvic inlet
Second:
- Determine the location of the fetal back
Third:
Determine which fetal part is lying above the pelvic inlet
Fourth:
Locate the fetal brow
- Performed after 30-32 weeks (T3)
Who is at highest risk of Thalassemia?
- Mediterranean
- SE Asian
- Western Pacific (pacific islanders)
How do you screen for thalassemia?
- CBC
- Hb electrophoresis or high pressure liquid chromatography
Who is at high risk of sickle cell?
- African
- Caribbean
Who is at high risk of cystic fibrosis?
- Family history of CF or condition closely associated (like male infertility)
How do you screen for cystic fibrosis?
CFTR gene DNA analysis
- cystic fibrosis transmembrane conductance regulator gene
- Codes for ion channel that conducts chloride
How do you screen for sickle cell?
- CBC
- Hb electrophoresis or HPLC
Who is at high risk of parvovirus B19? what tests would you order on someone at risk?
1)
- Someone with exposure to small children (at home, work, etc..)
- Showing symptoms such as febrile illness with rash or arthopathy
2) Parvovirus IgM and IgG
- IgM indicates acute infection
- IgG is produced shortly after infection and persists for life
How would you interpret a parvovirus B19 test showing
1) Positive IgM and IgG
2) Positive IgG and negative IgM
1) Acute infection
2) Immune, was exposed in the past, no recent infection
Your patient has positive IgM for parvovirus what is the next step? How do you counsel her?
- This indicates acute infection in the mother
- Next step is PCR testing of maternal serum for parvovirus DNA
- No increased risk of fetal abnormality, but increased risk of hydrops fetalis and fetal loss
When is the uterine fundus at the level of the pubic symphysis?
12 weeks
When is the uterine fundus at the umbilicus?
20 weeks
What should the symphysis fundal height be between weeks 20 and 36?
+/- 2cm of the gestational age
When is the uterine fundus at the sternum?
37 weeks
When should a dating ultrasound ideally take place?
Between weeks 8 and 12
- using crown-rump length
What is nuchal translucency? What does its measurement tell you? When do you check it?
- Measures the amount of fluid behind the neck of the fetus
- Early screen for trisomy 21
- May also detect cardiac and other aneuploidies like Turner
- Scan done between 11 and 14 weeks (Typically try to overlap the dating U/S and nuchal scan so week 11 or 12)
- Also the NT scan relies on having accurate dates so a dating ultrasound should be done
When is a growth and anatomy u/s scan done?
- between 18 and 20 weeks
What is noninvasive pre-natal testing? When is it performed?
Analysis of maternal blood for circulating fetal cells
- if detected use fetal DNA to assess for chromosomal abnormalities
- Done at 10 weeks ($ in ontario, but covered in women over 35 years)
What are the disadvantages of non-invasive prenatal testing?
1) Low specificity
- All positive results still must be confirmed with amniocentesis
2) Less sensitive for trisomy 18 and 13
3) Doesn’t screen for NTD
Describe the direct and indirect coombs tests. Which is used in prenatal screening?
Coombs reagent is an antibody made in an animal against the autoantibodies attacking Rh antigens
1) Direct
- Blood is taken from the patient
- Coombs reagent is added
- If there are autoantibodies against the Rh antigen present, the coombs reagent will bind causing agglutination
* Looking for autoantibodies bound to patient’s RBC *
2) Indirect
- Blood is taken from the mother, plasma is separated
- Rh+ blood is added to maternal plasma
- If the mothers plasma contained autoantibodies against Rh antigen, the blood will agglutinate
* Looking for autoantibodies in maternal serum *
- Indirect used in pre-natal screening. Looking to see if mother has these autoantibodies which can cross placenta and destroy fetal RBC
The prophylactic administration of Rhogam is administered to which women and at what time?
- Administered to all Rh negative women who do not have alloimmunization
- Given at 28 weeks (start of third trimester)
- Reason being, 3rd trimester is most common period to have asymptomatic bleeding which could potentially lead to alloimmunization
- Also give to all Rh negative woman as above withing 72 hours of giving birth to Rh + child
Atypical antibodies capable of producing hemolytic disease of the newborn are identified on prenatal screening how do you proceed?
- Serial titres of antibody levels
- Referral to tertiary center
- Early delivery if appropriate
How do you perform a pap smear on a pregnant woman?
- Do not insert the cervical broom into the cervical os after 10 weeks gestation
What is first trimester screening? (FTS) When is it done? What does it involve, What does it test for?
1) First trimester screening (FTS)
- Measured between 11 weeks, 0 days and 13 weeks 6 days
a) Pregnancy associated plasma protein A (PAPP-A)
b) B-hCG
c) Nuchal translucency
* Tests for trisomy 21, trisomy 18
* U/S also screens for anencephaly
What screening options are available in the second trimester? What do they involve, what do they test for? When can it be done?
Maternal serum screening
- Maternal serum alpha fetoprotein (MSAFP)
- B-hCG
- Estriol
- Inhibin A
2) Test for Trisomy 18, 21 and open NT defects
3) Can be done between 15 and 20 weeks - best at 16, when it is more accurate but there is still time to act on results
What is integrated prenatal screening (IPS)? When is it done? What does it involve, What does it test for?
1) Combined first and second trimester test
2a) First trimester
- PAPP-A
- NT
- B-hCG? i think
2b) Second trimester
- MSAFP
- B-hCG
- Estriol
- Inhibin-A
3)
- Trisomies 18 and 21
- ONTD
* Highest detection rate for downs and lowest false positive rates
How can prenatal genetic screening differ in women over the age of 35?
- They are offered invasive testing (amniocentesis or chorionic villous sampling) instead of others
What is chorionic villous sampling? When can it be done?
- sample of the chorionic villi is removed and sampled for testing
- tests for chromosomal abnormality and is definitive
- Can be done between 10 and 12 weeks gestation
What is amniocentesis and when can it be done?
- taking sample of the amniotic fluid for testing
- used as definitive testing for chromosomal abnormality
- Can be done from 15-16 weeks and onward
When and how is a patient screened for gestational diabetes in a normal pregnancy?
- Between 24 and 28 weeks
- with 50g OGCT
When is GBS screening done?
- 35-37 weeks
What results would you expect on a FTS of a down syndrome pregnancy?
1) Increased NT
2) Increased B-hCG
3) Decreased PAPP-A
What would you expect on a FTS of an edward syndrome pregnancy?
Trisomy 18
1) Increased NT
2) DECREASED B-hCG
- this is what differs from downs
3) Decreased PAPP-A
What would you expect on a MSS of a kid with down syndrome?
1) Decreased MSAFP
2) Increased B-hCG
3) Decreased unconjugated estrogen
4) INCREASED inhibin A
What would you expect on a MSS of an edward syndrome pregnancy?
Trisomy 18
1) Decreased MSAFP
2) DECREASED B-hCG
3) Decreased unconjugated estrogen
4) Decreased inhibin
What is Rhogam? How does it work?
- Rh IgG
- Binds of Rh antigens of the baby which prevents the mothers immune system from reacting
What is the Kleihauer-Betke test?
- Used to determine the extent of fetomaternal hemorrhage by estimating amount of fetal blood in maternal circulation
- Used to dose rhogam
