OBS: Fetal Medicine -- Twins Pregnancy

Question 1

USG Features to look for in twin pregnancy during DSS1

Answer 1

• Growth parameters: CRL
• Intertwin septum, T sign
• Nuchal translucency
• UtA Doppler

Question 2

Specific risks in MCDA compared to DCDA pregnancy

Answer 2

• TTTS, sFGR
• increased risk of preterm & IUD

Question 3

Routine management of an uncomplicated MCDA pregnancy

Answer 3

• General Mx: AN bloods, dating scan, DSS1, OGTT, GBS…
• Specific Mx:
  
  • Maternal tablet daily until 38w
  • Low-dose aspirin from 12w until 1w before EDC
  • Regular USG growth scan Q2w in 16-26w, then Q4w
  • Routine morphology scan
• MOD: IOL, or CS in 36-38w

Question 4

How to distinguish MCDA and DCDA pregnancy on USG?

Answer 4

MCDA: separate thin amnion, T-shape appearance
DCDA: thick inter-twin membrane septum, lambda sign

Question 5

Describe pathophysiology of TTTS

Answer 5

unbalanced blood flow in vascular anastomosis between MC twin placenta → one twin becomes the donor, the other becomes the recipient

Question 6

Describe pathophysiology of sFGR

Answer 6

unequal share of placenta in MC twins

Question 7

How could USG be used to differentiate between TTTS and sFGR?

Answer 7

TTTS: oligohydraminos in donor twin, polyhydramnios in recipient twin
sFGR: oligohydramnios in the sFGR twin, normal in the other

Question 8

Which is the most important USG growth parameter to decide whether a fetus has grown up to potential?

Answer 8

Abdmoinal circumference

Question 9

What plane should AC be measured in?

Answer 9

transverse plane

Question 10

What anatomical landmarks should be used while measuring AC?

Answer 10

• Stomach bubble (left abdomen)
• Spine (3’ or 9’ o’clock)
• Both adrenal glands
• Ribs
• Umbilical vein segment (anterior midline), uniting with portal sinus

Question 11

What is the risk if one co-twin is dead in the uterus?

Answer 11

Drawing all blood from live twin → severe hypotension → IUD

Question 12

At 30 weeks, USG scan now shows one co-twin with AC below 3rd percentile and EFW below 10th percentile. How would you use USG results to guide your management for this condition?

Answer 12

DDx: TTTS, sFGR
* Measure MVP for oligohyramnios (<2cm) in this twin, check if the other twin has polyhydramnio
* Measure AC, HL, HC, BPD (thus EFW) for the other twin
* UmA, DV, MCA Doppler for the other twin
* Look for placental insertion site
* Any other structural abnormalities
* Site of placenta, distance between insertion sites, cervical length to determine risk & feasibility of in-utero interventions
Mx:
1. TTTS: Fetoscopic laser coagulation, Selective fetal reduction, Repeated amnioreduction
2. sFGR: Fetoscopic laser coagulation, Selective fetal reduction

Question 13

What is the most important factor influencing the accuracy of the NIPT results for a DCDA mother?

Answer 13

fetal fraction

Question 14

One of the fetus <3rd centile and EFW 20% less than co-twin, name 2 fetal investigation results that will help you in deciding the risk of IUD that worth immediate delivery.

Answer 14

Umbilical artery doppler (REDF), CTG / fetal heart rate (bradycardia)

Question 15

That twin (DCDA) dies at 34 weeks. Will you deliver the co-twin?

Answer 15

Immediate delivery if the IUD affects both. Otherwise deliver at term