Algorithm-Based Fetal Gender Determination Using X and Y Mini-Short Tandem Repeats at Early Gestational Ages

Background: Detection of fetal DNA in maternal blood has been examined by many research groups for a few years; thereby, scientists have a shorter way to take to approach prenatal diagnosis of abnormal pregnancies. The Y chromosome sequences have recently become the most common applicable indices for fetal sex determination. Objectives: We conducted an algorithmic X and Y mini-Short Tandem Repeats (STRs) genotyping method that could solve the problem of false negative (no detection of Y sequences) results of previous methods. Patients and Methods: Blood samples were obtained from 106 pregnant women and their spouses. Conventional PCR amplified 19 mini-Short Tandem Repeats (STRs) and three non-STR markers, which were subsequently genotyped by the means of Polyacrylamide gel electrophoresis (PAGE). Results: Sensitivity and specificity of the mini-STR genotyping method for fetal DNA detection were calculated (95.9% and 98%, respectively) with a confidence interval of 95%. In addition, sensitivity and informativeness were computed for each of the single mini-STR markers in our conventional PCR method. We also introduced the minimum number of mini-STRs needed to reach maximum validity for fetal gender determination in clinical settings. Conclusions: Algorithm-based mini-STR genotyping method significantly increases the reliability (sensitivity and specificity) of gender determination using free fetal DNA and could be applied in prenatal clinical testing.