Aim and objective: To create crown-rump length (CRL)-based biometric chart for fetus in the first trimester among the Indian population.
Material and methods: Cross-sectional data were obtained from 400 singleton pregnancies between 11 and 14 weeks gestation with a normal outcome. Linear regression models were constructed; the mean and SD were derived as a function of CRL.
Results: There was a positive correlation of CRL with nuchal translucency (NT) (y = 0.0102x + 0.6307 R2 = 0.1177), biparietal diameter (BPD) (BPD = 0.032*CRL +0.185 R2 = 0.765), occipito-frontal diameter (OFD), lateral ventricular diameter (LV), abdominal circumference (AC) (AC = 0.944*CRL +9.684 R2 = 0.668), femur length (FL) (FL = 0.222*CRL -4.734 R2 = 0.661), fetal weight (FW) (FW = 1.328*CRL -10.41 R2 = 0.662). The regression models and centile charts of NT, BPD, OFD, LV, AC, and FW were constructed. Taking FW as the independent variable, a linear equation of BPD, AC, and FL to calculate weight was constructed.
Conclusions: The first-trimester centile charts of fetal parameters can be used as a reference for Indian population in the determination of gestational age or other adverse outcomes.
Keywords: Ultrasound; biparietal diameter; first trimester; nuchal translucency.