Fetal Medicine Foundation First Trimester Screening

The Fetal Medicine Foundation
The biochemical markers used in the first trimester beta-hCG and PAPP-A show the following trends in
cases with chromosome abnormalities:
βhCG
T21 ↑ ↓
T18 ↓ ↓
T13 ↓ ↓
Triploidy (paternal) ↑↑↑ ↓
Triploidy (maternal) ↓↓ ↓↓
Sex chromosome abn → ↓
PAPP-A
The gestational age used for the calculation of biochemical risk must be derived from the CRL and is
calculated automatically by the software on the basis of the CRL at the time of the 11 – 13 +6 weeks
scan and extrapolated back to the time when the blood was taken if the scan is not performed at the
same time as the blood test.
The program will accept biochemical measurements processed by Brahms Kryptor and Delfia Xpress,
converting these measurements into MoMs. If any other assay system is used, the MoMs rather than
whole values need to be entered, but as the FMF has not certified the laboratory method, it cannot
approve the risk (see the Registered laboratories section of the FMF website www.fetalmedicine.com).
The software user will see a message on the screening saying that Fetal Medicine Foundation has not
approved the biochemical assay used to generate this risk.
Laboratories can manually adjust their medians by 10% if they notice a continuous increase or
decrease of their MoM values.
Recent data suggests that pregnancies with low PAPP-A (