The Effect of Inhibin A on Prenatal Screening Results for Down Syndrome in the High Risk Czech Pregnant Women.

BACKGROUND: Currently, prenatal testing is based on an ultrasound examination, the testing of certain biochemical markers and, most recently, also on the analysis of fragments from the extracellular DNA of the fetus in the mother´s blood. The aim of this work was to verify whether inhibin A testing during pregnancy can help influence the risk distribution of Down syndrome screening results in high risk population and thus possibly reduce the number of unnecessarily invasive procedures, or for better stratification of risks when deciding on non-invasive DNA testing. METHODS: The concentrations of inhibin A were measured using a chemiluminescent immunoassay in two groups of screening tests. The first group (triple test) included a total of 277 pregnant women; the second group (integrated test) included 91 pregnant women. Risk assessments of screenings were performed using Alpha software, LMS. RESULTS: The resulting risk for pregnant women without the determination of inhibin A was higher or equal to 1:300 (triple test) and 1:150 (integrated test). Inhibin A was then measured in the monitored groups and the risk was recalculated. In the first group (triple test) the risk was lower than 1:300 in 152 pregnant women and in the other group (the integrated test) in 47 pregnant women. At the end of the study, all results were compared with the outcome of the pregnancy. CONCLUSIONS: The results obtained show that the inclusion of inhibin A in screening protocols reduces the number of positive results in high risk population screened without inhibin A.

Importance of the integrated test in the Down's syndrome screening algorithm.

OBJECTIVE: In the Czech Republic, over 97% of all pregnant women undergo some type of antenatal screening for Down's syndrome. In about 95% of cases with a confirmed fetal chromosomal abnormality, the pregnancy is terminated. The most commonly used test is the first trimester combined test. We investigated the impact of implementing an integrated sequential test to improve the detection of Down's syndrome pregnancies. METHODS: Data on the incidence of congenital defects, number of births, and affected pregnancies terminated are recorded in the National Registry of Congenital Anomalies. Anonymous data on cases of Down's syndrome diagnosed antenatally or postnatally between 2010 and 2015 in one of the large antenatal care centers were analyzed. RESULTS: There were 600 diagnoses of Down's syndrome (5.7 per 1000 births), 90% of which were made antenatally. Of antenatally detected cases, 80% were indicated for diagnostic procedure by multimarker screening results. In the multimarker screen positive group, 75% cases were first trimester positive and 25% second trimester positive (most of these had positive integrated test results). Among Down's syndrome cases indicated for antenatal diagnosis by multimarker screening results 6.25% (n = 26) were first trimester negative, and became positive after integration with the second trimester screening results. CONCLUSIONS: Results from five major Czech antenatal centers confirm that an integrated sequential test would detect 80-85% of Down's syndrome fetuses in the first trimester and at least an extra 5-10% of Down's syndrome pregnancies in the second trimester of pregnancy. These are important data that should be considered in implementing the national antenatal screening program.

Maternal plasma DNA testing for aneuploidy in pregnancies achieved by assisted reproductive technologies.

PURPOSE: We sought to compare measurements of circulating cell-free DNA as well as Down syndrome test results in women with naturally conceived pregnancies with those conceived using assisted reproductive technologies. METHODS: Data regarding assisted reproductive technologies were readily available from seven enrollment sites participating in an external clinical validation trial of nested case/control design. Measurements of circulating cell-free fetal and total DNA, fetal fraction (ratio of fetal to total DNA), chromosome-specific z-scores, and karyotype results were available for analysis. RESULTS: Analyses were restricted to 632 euploid (5.2% assisted reproductive technologies) and 73 Down syndrome (13.7% assisted reproductive technologies), including 16 twin pregnancies. No differences were found for fetal or total circulating cell-free DNA, or for the fetal fraction in euploid (P = 0.70) or Down syndrome (P = 0.58) pregnancies by method of conception. There appeared to be systematic z-score reductions for chromosomes 21, 18, and 13 in assisted reproductive technologies versus natural euploid pregnancies (P = 0.048, 0.0032, and 0.36, respectively). CONCLUSION: Assisted reproductive technologies and naturally conceived pregnancies contribute similar levels of circulating cell-free DNA into maternal circulation. Small differences in the z-scores of pregnancies achieved by assisted reproductive technologies were observed and do not appear to be test-related artifacts. However, the findings need confirmation before any consideration of changes to testing and reporting protocols.