Evaluation of the adequacy of care for individuals with diabetes in Brazil: The intersection between gender, race, and socioeconomic profile.

In the early 1990s, increased nuchal translucency (NT) was first identified as a sonographic marker for fetal chromosomal abnormalities in the first trimester, particularly for the detection of Down syndrome (trisomy 21) []. Fetal NT measurement is a clinically significant parameter assessed by ultrasound between 11 and 13 weeks of gestation. Currently, an NT thickness of ≥3.5 mm, corresponding to the 99th percentile irrespective of gestational age and fetal crown-rump length (CRL), is recognized as one of the most sensitive indicators of fetal chromosomal abnormalities and is a definitive indication for invasive prenatal diagnosis []. Fetuses with increased NT have an elevated risk of chromosomal aneuploidy, pathogenic copy number variations (pCNVs), prenatal or perinatal death, and other adverse pregnancy outcomes [–]. Moreover, the risk of fetal abnormalities and adverse outcomes is proportional to the degree of NT enlargement. When increased NT is detected in the first trimester, invasive prenatal diagnostic techniques-such as chorionic villus sampling (at 11–13 weeks) or amniocentesis (typically performed at approximately 20 weeks of gestation) are often employed to exclude chromosomal defects. Recent studies have reported that increased NT is associated with not only chromosomal aneuploidy but also chromosomal CNVs, cardiac and other structural anomalies, and single-gene disorders (e.g., Roberts syndrome and syndrome) [–]. In addition to prenatal screening, NT measurement and maternal age are independent indicators in first trimester [].A cohort analysis and literature review found that fetuses with an NT of 3.0–3.4 mm have a high risk of 1:7.4 for a chromosomal aberration, of which 69% involve chromosomes 13, 18, and 21 []. However, the cutoff value for defining increased NT as an indication for invasive prenatal diagnosis remains inconsistent and varies between countries. For example, fixed cutoff values such as ≥2.5 mm, ≥ 3.0 mm, and ≥3.5 mm are used in different national guidelines []. These inconsistent criteria have led to controversial data and analyses, thereby limiting the clinical utility of NT measurement in prenatal diagnosis. In accordance with clinical practice, the present study adopted a cutoff value of 2.5 mm to define NT thickening [,]. For many years, standard karyotyping has been considered the “gold standard” for detecting chromosomal abnormalities in prenatal diagnosis. This technique can identify numerical abnormalities and balanced translocations–such as free trisomies, Robertsonian translocations, and large structural aberrations (>5–10 Mb)–but it requires prolonged cell culture and offers limited resolution for cytogenetic detection [,]. In contrast, SNP-array enables the detection of CNVs across the whole genome. This method can identify chromosomal imbalances, including aneuploidy and unbalanced rearrangements, with a particular advantage for detecting microdeletions and microduplications that cannot be resolved by standard karyotyping [,]. Therefore, we conducted a retrospective analysis to summarize the clinical features, chromosomal abnormalities, and obstetric outcomes associated with increased NT in 180 fetuses, aiming to provide a clinical reference for prenatal diagnosis.