Introduction: To evaluate the performance of first trimester nuchal translucency scan screening among pregnant women in Nigeria.
Methods: A prospective observational and questionnaire based study involving 510 pregnant women between 11(+0) and 13(+6) weeks. Routine counselling and nuchal translucency measurement was conducted using the FMF, London guidelines. Chorionic villous sampling was done at NT ≥ 2.5 mm or ≥ 95th centile.
Results: Five hundred and ten out of 542 (94.1%) were analysed, mainly referred by health care workers (87.2%) and from predominantly private facilities (94.3%). The number of NT scans performed increased in successive years with corresponding decrease in the mean scanning time. Scan was successfully completed at first attempt in (96.5%), with mean scanning time of 28.3 minutes. Nuchal translucency increases with gestational but not maternal age. The median and 95th centile at 11(+0) week was 1.2mm and 1.7 mm and at 13(+6) weeks was 1.5 mm and 2.2 mm. Using a cut-off of ≥ 2.5 mm or ≥ 95th centile, 17 (3.3%) screened positive. Three out of the 17 had invasive testing and 2 (DR = 66.7%) were confirmed trisomy 21, with a false positive rate of 5.9%. Although majority (86.4%) were willing to have invasive testing, only few (3 or 17.6%) of the high risk group had testing.
Conclusion: The study demonstrated that NT scan is feasible as a screening tool in pregnancy in Nigeria. Measures of improving utilization include wider dissemination of information, provision of dedicated NT clinics and manpower training.
Keywords: Down syndrome; Nuchal translucency scan; Performance.