**4. Obstetric markers in paternity suits**

Paternity testing in the prenatal period could be required in cases of pregnancy resulting from rape. Earlier, the paternity testing depended on invasive procedures such as chorionic villus sampling and amniocentesis. These procedures could pose a risk to the wellbeing of the mother and fetus. In order to find a relatively safer testing method, non-invasive methods using the cell free fetal DNA (cffDNA) were investigated [19].

Initially the genetic markers investigated were short tandem repeat (STR) loci. But, the increased stutter amount hindering allelic assignments and decreased size of DNA fragments- maternal & fetal proved to be a hindrance [20]. Also only Y-chromosome STRs (Y-STRs) could be used which restricted the application to male fetuses only and not in female fetuses. The chances of false paternity exclusions were increased [21].

Then the Single nucleotide polymorphisms (SNPs) were investigated. A recent study done by Tam et al. developed a systematic SNPs selection procedure which reduced the number of target-SNPs for sequencing analysis to an average of 148 effective SNPs to calculate the probability of paternity. But the possible drawback is that in order to perform the test, a large number of loci is required [22]. But this is the mainstay for noninvasive paternity testing as of now.

With the number of SNPs to be tested on an average being 148, it can be cumbersome. So research is on to find a better genetic marker. Hence, the use of microhaplotypes is being researched. Microhaplotypes are the regions of ~200 bp containing two or more SNPs and at least three different haplotypes. Microhaplotypes with only 15 regions and with admixtures of DNA are being researched to determine paternity in a non-invasive manner [23].

### **5. Medicolegal implications**

Obstetric markers is emerging as an important aspect in the forensic diagnostics. The pregnant women may face crimes like rape, physical harm against them. While, they may undergo criminal abortions, illegal feticide or have a substance abuse issue for which they can be held liable. The various obstetric markers- use of mRNA in bloodstains, use of biomarkers in substance abuse or the noninvasive genetic

markers for paternity testing, play an important role in solving the investigations and cases. Amongst the tests performed to determine if the bloodstain is that of a pregnant woman, the detection of mRNA of hPL is superior to other DNA analysis methods. Amongst the non-invasive paternity testing methods which is gaining prominence, the SNP detection is far superior to the STR detection. The emergence of use of Microhaplotypes which would further simplify the paternity detection is still under research.
