Prenatal screening for anueploidies in the first trimester: Audit to a Fetal Medicine Centre with specialized Laboratory in Mexico

Screening for aneuploidies using ultrasound and biochemical first trimester markers has an expected performance if the qualification requirements are fulfilled. To describe the first trimester markers in Mexico through the audit to a Fetal Medicine Centre and Laboratory. Descriptive study conducted with the audit method of ultrasound and biochemical markers in pregnancies that prenatal screening tests in the first quarter were made between 11 + 1 and 14 + 1 weeks pregnant patients who came to the Laboratorio del Centro Médico para Atención Fetal Especializada. In 17 months n=1020 pregnancies, 962 (94.3%) single, 55 (5.4%) doubles, and 3 (0.3%) triplets. Median maternal age of 33.8 years (16-52), 413 (40.5%) > or = 35 years. 1080 foetuses with 1009 valid measurements of nuchal translucency (29.8% at external cabinets), 54% >p50; 7.3% >p95, and 1.6% > p99. Out of 1555 sera processed at the Laboratory (f-beta-hCG and PAPP-A, Roche), 641 (41.2%) were interpreted at external centres. In 914 sera the f-beta-hCG MoM were p50 = 0.72, 3.2% >p95; for PAPP-A, p50 = 0.89, 9.0% < p5. There were 850 combined tests, and in 745 an additional marker was added; the IP ductus venosus median was 0.99 MoM. A risk > or =1 in 100 resulted in 50 foetuses (4.6%); 27 underwent invasive procedure at our Centre, 19 normal karyotypes, and 8 abnormal as: 3 trisomy 21 and 5 diverse aneuploidies. The qualification requirements are fulfilled for nuchal translucency, ductus venosus, and the combined test; 1 out of 3 invasive procedures resulted an aneuploidy; the estimated false positive rate is 3.9%. The Laboratory will adjust the median values of the biochemical markers. A cohort study has begun.