The objective of the present study was to evaluate the influence of second-trimester ultrasound markers on the incidence of Down syndrome among pregnant women of advanced maternal age. This was a retrospective cohort study on 889 singleton pregnancies between the 14th and 30th weeks, with maternal age ≥ 35 years, which would undergo genetic amniocentesis. The second-trimester ultrasound assessed the following markers: increased nuchal fold thickness, cardiac hyperechogenic focus, mild ventriculomegaly, choroid plexus cysts, uni- or bilateral renal pyelectasis, intestinal hyperechogenicity, single umbilical artery, short femur and humerus length, hand/foot alterations, structural fetal malformation, and congenital heart disease. To investigate differences between the groups with and without markers, nonparametric tests consisting of the chi-square test or Fisher’s exact test were used. Moreover, odds ratios with their respective 95% confidence intervals were calculated. Out of the 889 pregnant women, 131 (17.3%) presented markers and 758 (82.7%) did not present markers on the second-trimester ultrasound. Increased nuchal fold ( ) and structural malformation ( ) were the markers most associated with Down syndrome. The presence of one marker increased the relative risk 10.5-fold, while the presence of two or more markers increased the risk 13.5-fold. The presence of markers on the second-trimester ultrasound, especially thickened nuchal fold and structural malformation, increased the risk of Down syndrome among pregnant women with advanced maternal age. 1. Introduction Although chromosomal abnormalities occur at low frequency in the population, around 0.5% to 2% [1], they contribute significantly to increased perinatal morbidity and mortality [2]. Trisomy is the most frequent chromosomal abnormality, especially of chromosome 21, that is, Down syndrome. Since Down syndrome is difficult to diagnose during the prenatal period and because there is the possibility of survival after birth, it contributes to increasing the statistics of cases of mental retardation. Thus, prenatal screening is important, especially among women of advanced maternal age, that is, greater than or equal to 35 years [3]. The presence of certain alterations on the second-trimester ultrasound, called markers, enables increased sensitivity in screening for trisomy 21. This can reach up to 84% and possibly surpass 90% when heart markers are included [4–7]. The challenge is to distinguish the presence of these small alterations on the second-trimester ultrasound, between chromosomally
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