Instructions
You are a medical student on placement in the antenatal clinic at King Edward Memorial Hospital. Your next patient is Thuy Dang, 38, an accountant in her second pregnancy, referred urgently by her GP after a screening blood test. Her result is below.
Explain the result and your initial management plan to the patient
- You do not need to take a history or examine the patient.
- The examiner will ask you one question at the end.
From the GP referral
Second pregnancy; 12 weeks 2 days today by a dating scan at 7 weeks, which showed one baby. Daughter, 4, well after a normal pregnancy and birth. No medical problems. Booking blood tests normal.
Cell-free DNA screen (blood at 10 weeks 3 days)
Trisomy 21: high chance (abnormal). Trisomies 18 and 13: low chance (normal).
Fetal fraction
9% (adequate; reference above 4%). Sex chromosomes not analysed.
Estimated chance this pregnancy has trisomy 21
About 9 in 10 (from this result and her age)
Cell-free DNA screening report (blood taken at 10 weeks 3 days)
| Item | Value | Reference range |
|---|---|---|
| Fetal fraction | 9% | >4% |
| Trisomy 21 | High chance | - |
| Trisomy 18 | Low chance | - |
| Trisomy 13 | Low chance | - |
| Estimated chance this pregnancy has trisomy 21 (from this result and her age) | About 9 in 10 | - |
Sex chromosomes not analysed (not requested).