Changes to timing of maternal blood collection for CFTS

Effective screening for all major aneuploidies can be achieved in the first trimester of pregnancy using the Combined First Trimester Screen (nuchal translucency ultrasound + maternal serum biochemistry markers of PAPP-A and free βhCG) with a detection rate of 94% with a 5% false-positive rate. RANZCOG recommends that screening should be offered to all women.

Previously serum biochemistry was collected 3 days prior to ultrasound examination. However new research has demonstrated that serum biochemistry at 9 -10 weeks improves the detection rate from 90% to 94%.

Ideal Dates:

  • Maternal serum biochem at 10 weeks
  • Nuchal translucency ultrasound at 12 weeks

Prenat Diagn 2011; 31: 7–15. Kypros H. Nicolaides* Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital, London, UK and Dept. of Fetal Medicine,University College Hospital, London, UK