Ultrasonographic analysis of biparietal diameter as an indicator of gestational age in North Indian fetuses

Background: Clinical data such as menstrual cycle or uterine size often are not reliable parameter for pregnancy dating. Sonographic measurements of the fetus provide information about gestational age, growth and expected date of delivery. Aims: To develop a reference chart to estimate gestational age by ultrasonographic measurement of fetal bi-parietal diameter (BPD) and to find out correlation between two variables. Material and Methods: Cross sectional study was conducted on among 750 pregnant women of gestational age of 14-40 weeks, attending the Obstetrics and Gynaecology out-Patient department during one year period. Each fetus was ultrasonographically measured for BPD, the mean was used in subsequent statistical analysis. Statistical Analysis: It was done by the software SPSS version 21.0. A p-value < 0.05 considered to be significant. The previously published nomograms were compared by using unpaired t-test. Correlation & regression analysis has been done for BPD and GA. Results: Out of total 750 participants, 97.6% females confirmed their pregnancy by urine pregnancy test, 22.9% had dating scan, mean height was 163.004 cm. On ultrasound examination 78% participants had vertex, 7.6% had breech and 14.4% had variable presentation of fetus.Mean BPD increases 3.07 mm per week from 14to30 weeks and 1.93 mm per week from 31 to 40 weeks. For establishing a relationship between two variables GA & BPD, the correlation & regression analysis has been done.Sigmoid regression equation was the best for this study. Conclusions: Data showing that North Indian fetuses are smaller than European fetuses after 22 weeks gestation.