OBS: Antenatal Care -- Thalassaemia

Question 1

DDx of low MCV and further investigations

Answer 1

DDx: iron deficiency anaemia, anaemia of chronic disease, sideroblastic anaemia (e.g. lead poisoning), thalassaemia (carrier)
Ix:
1. MCV (mean corpuscle volume)
- if **<80**
1. Hb pattern to confirm status
1. HPLC (high performance liquor chromatography)
- HbA2 >3.5% ⇒ diagnostic of β-thalassaemia

                *not useful for diagnosis of α-thalassaemia*
                
        2. **Alpha IC strip** (immune-chromatographic strip)
            - `+ve` ⇒ diagnostic of α-thalassaemia
            - `-ve` → proceed to genetic tests
        3. `if alpha IC strip -ve` Alpha genotyping
    2. **Iron profile** to look for any co-existing IDA
    3. **MCV +/- Hb pattern** for partner

Question 2

Diagnosis of beta-thalassaemia trait

Answer 2

HPLC: HbA2 >3.5%

Question 3

How to counsell a couple who are both alpha thalassaemia carriers?

Answer 3

Explain the probability for fetus to be alpha thalassaemia major is 25% (assuming SEA deletion)

Prenatal diagnosis:
1. USG monitoring for signs of fetal anaemia Q2W between 12~24w **first-line**, but for α only
1. Cardiomegaly / Cardiothoracic ratio

    *90% sensitivity before 14w*
    
2. **Placental thickening**
3. **↑ MCA PSV**

`if +ve` proceed to invasive diagnostic procedure

2. Invasive diagnostic procedure: *refer to section below for decision making*
   
   1. CVS, OR
   2. Amniocentesis, OR
   3. Cordocentesis for Hb pattern analysis for α only
   since β-thal does not manifest in-utero, invasive procedure is inevitable for diagnosis

Consider IVF with pre-implantation genetic diagnosis

Take 5mg folic acid throughout pregnancy

Question 4

What is the most common genotype for alpha thalassaemia trait?

Answer 4

SEA deletion

Question 5

Implication of hydrops fetalis to mother

Answer 5

increased chance of PET

Question 6

How to prevent alpha thalassaemia in next pregnancy?

Answer 6

IVF followed by pre-implantation genetic analysis, transfer of unaffected embryos

Question 7

What are the management options for confirmed alpha thalassaemia? Pros and Cons?

Answer 7

1. Non-aggressive approach:
   (Before 24w) TOP
   (After 24w) Early IOL to induce preterm birth without neonatal resuscitation
   Pros: reduce risk of PET, reduce risk of obstructed labour due to hydrop, no complications of treatment
   Cons: fetus not viable
2. Aggressive approach:
   a. Repeated in-utero transfusion Q2~4w
   b. Post-natal regular transfusion / BM transplant
   Pros: fetus kept alive
   Cons: risk of neurodevelopmental delay, hypoxic anatomical abnormalities

Question 8

EIA and VDRL +ve. What are the further tests? How do they affect the management?

Answer 8

Specific Treponemal Diagnostic Tests: FTA-abs, TPPA
If -ve, EIA & VDRL are false positives
If +ve & not treated before, diagnosed as latent syphilis. Treat with IM Penicillin

Question 9

Risk factors for transverse fetal lie

Answer 9

Maternal: multiparity (lax uterus), lower segment obstructed by SOLs
Obstetrics: multiple pregnancies, polyhydramnios, PROM when fetal is in transverse lie
Fetal: Fetal abnormalities

Question 10

Complications of ECV

Answer 10

1. Transient fetal decelerations
2. APH / Placental abruption
3. ROM +/- cord prolapse
4. Uterine rupture
5. Acute fetal distress