Ultrasound Obstet Gynecol. 2013 Dec 6. doi: 10.1002/uog.13270. [Epub ahead of print]
Potential diagnostic consequences of applying non-invasive prenatal testing (NIPT); a population-based study from a country with existing first trimester screening.
Non-invasive prenatal testing (NIPT) could be an alternative to traditional karyotyping. NIPT tests for trisomies 21, 18 and 13 and sex chromosome aneuploidies. We aimed to determine the risk of missing other abnormal karyotypes of likely phenotypic significance by NIPT.
A retrospective population-based analysis of all singleton pregnancies booked for combined first trimester screening (cFTS) in Denmark over a four-year period. Data concerning maternal demographics, cFTS and prenatal or postnatal karyotypes were collected from the Danish Fetal Medicine database. Karyotypes were classified according to whether the chromosome anomaly would have been detected by NIPT, and whether they were likely to affect phenotype.
cFTS was completed in 193638 pregnancies. 10205 (5.3%) had cytogenetic or molecular analysis performed. 1122 (11.0%) had an abnormal karyotype; 262 (23.4%) would been missed by NIPT, but would likely have been clinically significant. The prevalence of such an 'atypical abnormal karyotype' was increased in women above 45 years, in pregnancies with increased NT (≥3.5mm), with abnormal levels of ß-hCG (<0 .2="" 1.6="" 3="" abnormal="" and="" atypical="" cohort="" factors="" high-risk="" in="" karyotypes="" mom="" more="" of="" om.="" one="" or="" p="" papp-a="" present="" prevalence="" the="" these="" this="" was="" women="">
A significant proportion of karyotypic abnormalities will be missed by NIPT. Women of advanced maternal age, or with increased NT, or abnormal biochemistry have a higher risk of having a fetus affected by an atypical abnormal karyotype and need to be counselled accordingly when considering NIPT.
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NIPT, chromosomal anomaly, free fetal DNA, prenatal diagnosis, prenatal screening
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