Investigation of non-invasive prenatal testing, positive predictive value, and the relationship between individual maternal characteristics, assisted reproductive technology, and twin fetuses with chromosomal disorders, a cross-sectional study

Document Type : Original Article


1 Behbahan Faculty of Medical Sciences and Health Services, Behbahan, Iran

2 Department of animal biology, kharazmi university, Tehran, Iran

3 Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran

4 Department of Midwifery, Falavarjan Branch, Islamic Azad University ,Isfahan, Iran



Objective: Non-invasive prenatal testing (NIPT) is widely used as a new screening method for screening for fetal chromosomal aneuploidy. This study aims to evaluate the relationship between first trimester screening (FTS) and positive NIPT estimate and positive predictive value (PPV), as well as the relationship between advanced maternal age (AMA), race, smoking and use of assisted reproductive technology (ART) and examination of twins with the incidence of Tr21, Tr18, Tr13 and SCA is discussed.

Methods: This cross-sectional study was conducted on 5292 pregnant women who referred to the Narges Genetics Laboratory in Ahvaz for FTS and NIPT. Nuchal translucency (NT), crown–rump length (CRL), percentage of nasal bone presence and fetal heart rate (FHR) were measured by ultrasound evaluation. Biochemical biomarkers pregnancy-associated plasma protein-A (PAPP-A) and free beta of human chorionic gonadotropin(freeβhCG) were assessed using an immunoassay analyzer in the chemiluminometer package. Cell-Free(Cf) DNA was extracted from maternal plasma. Complete exome sequencing was applied to the applicants by an ion semiconductor sequencer using cf DNA. Finally the karyotype of the fetus was checked.

Results: There was no significant association between CRL, nasal bone percentage, FHR, BMI and positive NIPT (P=0.45). There was a significant association between NT, mean age, PAPP-A, fβhCG and positive NIPT(P=0.04). We encountered 102 positive cfDNA tests. The cfDNA PPV test showed 92.3% for T21, for T18, T13 and SCA the PPV was 77.7%, 28.6% and 58%, respectively, there was a significant difference between the race of the mother,twin fetuses and the incidence of chromosomal abnormalities (P= 0.04). There was no significant difference between smoking, ART and chromosomal abnormalities (P=0.45).

Conclusion: Analysis of cf DNA with selective chromosome sequencing can correctly detect trisomy Tr21, Tr18, Tr13 and SCA with relatively high sensitivity. AMA, race and twins can be a risk factor for fetal chromosomal abnormalities.


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