Normogram of fetal nasal bone length in second trimester in Pakistani population

1. Normogram of fetal nasal bone length in second trimester in Pakistani population Ayesha Malik, Shama Munim Department of Obstetrics & Gynaecology, The Aga Khan University Hospital, Karachi - Pakistan Conclusion Introduction Methodology A cross sectional study was conducted from January 2004 to December 2011. Prospective as well as retrospective data was included. Down syndrome is the commonest chromosomal abnormalities in the newborn. Invasive testing is the only confirmatory procedure for its prenatal diagnosis. However invasive procedures have a miscarriage rate of 1%. Hence need for a screening test that has a high sensitivity for detection of Trisomy 21. Evidence is emerging for relationship between ultrasonographic absence or hypoplasia of nasal bone and trisomy 21 ,indicating that nasal bone length may be useful in screening for trisomy 21 in the first and second trimester . Morphometery of facial features including nasal bone length differs with ethnicity. Midtrimester fetal nasal bone length has been assessed in Chinese population and found to be shorter than their Western and African counterparts. Since no data has been published from South East Asia, we intend to construct a reference range for nasal bone length in healthy Pakistani fetuses. The measurement of nasal bone length is feasible in the second trimester. The reference range of NBL in Pakistani fetuses in the second-trimester of pregnancy was established. This forms a basis for further study on the use of fetal nasal bone measurement in the screening for aneuploidy in the Pakistani population. The study population was all fetuses having anomaly scan in Fetomaternal unit. Measurement of the fetal nasal bone was performed between 14-28 weeks. Scatter plots for nasal bone length as a function of gestational age and biparietal diameter were constructed. The 5th and 50th and 95 th percentile values were calculated for each gestational week period of 14-19,20-24 and 25-28 weeks Objective Results The study aimed to construct normograms for fetal nasal bone length in Pakistani foetuses The nasal bone length measurement showed a significant increase with gestational age (GA) (p <0.05). A linear relationship between nasal bone length and gestational age (NBL =-4.27 × GA + 0.639,R2= 0.258, p < 0.001) .