First Trimester Screening Tests Pregnancy and Trisomy 13 Syndrome, Sex Chromosome Aneuploidy in Iran: A Cross-Sectional Study.

Background: Trisomy 13 (T13) and sex chromosome aneuploidies (SCA) are the vital causes of congenital malformations. This study was performed to identify the T13 and SCA with screening tests in the first trimester of pregnancy. Materials and Methods: In this cross-sectional study, first-trimester combined screening was conducted on 2100 pregnant women referred to Narges Genetics Laboratory, Ahvaz, Iran. Evaluating the first trimester screening tests, including nuchal translucency (NT), crown--rump length (CRL) and pregnancy-associated plasma protein-A (PAPP- A), and free beta of human chorionic gonadotropin (fβhCG) was performed. For a definitive diagnosis of T13 and SCA syndrome, fetal karyotype was evaluated. Results: The average NT and CRL in high-risk group for T13 were 5.96 mm and 61.7 mm respectively and in high- risk groups for SCA were 3.7 mm and 75.9 mm, respectively. Significant correlation was observed among NT, CRL and T13, SCA (P<0.05). The average serum fβhCG and PAAP-A levels in high-risk group for T13 were 0.42 and 0.31, respectively. Significant correlation was observed between decrease fβhCG, PAPP-A and T13 levels and increase fβhCG levels and SCA levels (P<0.05). No Significant correlation was observed between PAPP-A levels and SCA levels (P>0.05). Conclusion: Using special software and karyotype testing, the prenatal screening tests based on the maternal age and gestational age in the first trimester of pregnancy may determine the major risk of fetal chromosomal abnormalities. [ABSTRACT FROM AUTHOR]