the association between serum biochemical markers and early amniocentesis in diagnosing chromosomal anomalies: a cross-sectional study in southern iran, 2021-2022

Background: efforts to improve prenatal diagnosis of down syndrome have been made, with amniocentesis representing an invasive procedure, and maternal serum biochemical markers are among the non-invasive options. this study aimed to examine the association between serum biochemical marker values and amniocentesis results in the prenatal diagnostics of down syndrome in early pregnancy.methods: in a cross-sectional study, data from pregnant women in the first trimester undergoing amniocentesis test for the diagnosis of fetal genetic diseases were collected during 2021-2022. maternal weight, maternal age, gestational age at nuchal translucency (nt) scan, nasal bone (nb) status, and serum chemical biomarkers—including pregnancy-associated plasma protein-a (papp-a), and beta-human chorionic gonadotropins (β-hcg) were assessed. results: of 1,987 amniocentesis cases, 96.5% were normal, and 3.5% were abnormal. down syndrome was present in approximately 3% of cases. maternal weight was significantly lower in the abnormal amniocentesis group than in the normal group. after adjusting for maternal weight, maternal age, nt, and β-hcg were significantly higher in the abnormal amniocentesis group, whereas papp-a was lower. the nb status did not differ between groups. a papp-a level of <0.42 multiple of median (mom) (sensitivity=90%, specificity=68%) and a β-hcg level of ≥1.52 mom (sensitivity=76%, specificity=70%) acceptably predicted down syndrome in abnormal amniocentesis cases. among the 69 abnormal amniocentesis cases, 49 cases had down syndrome; of these, 75.5% had a down syndrome risk of ≤1:100.conclusion: both β-hcg and papp-a had independent diagnostic value in predicting down syndrome in early pregnancy. it is recommended that a down syndrome risk of up to 1:100 warrant direct amniocentesis, while cases with a risk greater than 1:100 should be offered non-invasive alternatives.