Role of 1st trimester ultrasonography in detecting fetal abnormalities versus 20 weeks scan in high risk women

Aim: to find the role of first trimester usg in detecting fetal anomalies by taking 20 weeks scan as standard. methods: this cross-sectional descriptive study was carried out at gynaecology & obstetrics,lady willingdon hospital,unit 3,lahore from 4th april 2012 to 3rd oct 2012. six hundred and fifty cases were taken to evaluate the role of 11-14 weeks scan in the diagnosis of fetal abnormalities in high risk women by taking 20 weeks gestation as gold standard. results: majority of the women were between 21-25 years,with the mean age of 28.40±2.35 years anomalies mostly were detected at 12+1-13 weeks. prevalence of anomaly found is 11.69%. the most common anomaly detected was anencephaly. cases by fetal anomalies includes,21 (3.2%) fetuses with anencephaly,5 (0.8%) encephalocele,10 (1.5%) cystic hygroma,5 (0.8%) omphalocele with increased nuchal translucency,7 (1.1%) gastroschisis,4 (0.6%) megacystitis,3 (0.5%) multicystic kidney disease and 2 (0.3%) cardiac anomaly. total anomalies detected were 75 (11.5%). the total number of normal fetuses is 575 (88.4%). thirteen anomalous fetuses were not detected in the first trimester usg. three fetuses were with multicystic kidney disease,three with anencephaly + spina bifida,one with hydrocephalus,two with cardiac anomalies,two cystic hygroma with intra-abdominal cysts and two with megacystis. their detection percentage at first trimester corresponds to 0%,57.1%,50%,0%,33.3% and 50% respectively. fetal anomaly detection through first trimester usg had a sensitivity of 82.66%,the specificity 100%,positive predictive value of first trimester scan 100%,negative predictive value of 97.78% and diagnostic accuracy of 98%. conclusion: first trimester usg is effective in detecting fetal anomaly.