First trimester fetal ultrasound parameters associated with PAPP-A and fβ-hCG

Abstract

Objective: To study the association of fβ-hCG and PAPP-A measured at 11–14 weeks of gestation with delta crown-rump-length (dCRL), delta fetal heart rate (dFHR) and delta nuchal translucency (dNT). To calculate adjusted MoM taking into consideration these associations. Methods: Retrospective cross-sectional study on 5,536 singleton euploid pregnancies participating in a first trimester screening program for chromosomal abnormalities by nuchal translucency and maternal serum biochemistry. Adjusted MoM were calculated for fβ-hCG and PAPP-A and compared to the observed MoM (calculated by the Fetal Medicine Foundation screening algorithm). Results: fβ-hCG correlates positively with dCRL and negatively with dNT, whereas PAPP-A shows a positive correlation with dNT and a negative one with dCRL and dFHR. After adjustment for the ultrasound parameters, the median MoM values for fβ-hCG and PAPP-A changed from 1.02 and 0.92 observed MoM to 0.98 and 0.99 adjusted MoM respectively. The difference between the observed and adjusted MoM was statistically significant (p < 0.001). Delta CRL increases with gestation and this effect manifests mainly after CRL of 62 mm. Conclusions: Adjustment for dCRL, dFHR and dNT improves the calculation of MoM for fβ-hCG and PAPP-A. CRL measurement overestimates fetal size at the end of the screening period 11–14 weeks.

Keywords::

• Crown-rump length
• fetal heart rate
• nuchal translucency
• PAPP-A
• fβ-hCG
• ultrasound scan
• 11–14 weeks

Declaration of Interest: The authors report no conflicts of interest.