Reference centile charts of first-trimester aneuploidy screening & Doppler parameters for Indian population

Background & objectives: The risk estimation for foetal aneuploidies in the first trimester of pregnancy uses reference curves based on western data. The objective of this study was to construct the reference curves of first-trimester foetal aneuploidy screening parameters for the Indian women. Methods: Cross-sectional data were obtained from 1204 singleton pregnancies between the crown-rump length (CRL) of 40-84 mm. Linear regression models were constructed; the mean, median and standard deviation were derived as a function of CRL. Results: The mean value of CRL was 61.3 mm. The regression analysis showed a significant correlation between all variables and CRL (P< 0.001). There was a positive correlation of CRL with nuchal translucency (NT) (y=0.010x+0.629, R2=0.116) and pregnancy-associated plasma protein-A (PAPP-A) (y=0.107x?1.079, R2=0.173), whereas inverse correlation was seen with free ?-human chorionic gonadotropin (?-hCG) (y=?0.409x+75.025, R2=0.018) and Doppler parameters pulsatility index (PI) (y=?0.008x+1.924 R2=0.053). The centile charts of NT, PAPP-A, free ?-hCG and uterine artery (Ut A) Doppler PI were constructed. Interpretation & conclusions: The reference centile charts of first trimester aneuploidy screening along with Doppler parameters were derived in Indian pregnant women. These centile charts may be used as a reference for clinical use in Indian population.