Study Objective: To evaluate the effect of low molecular heparin (LMH) therapy on non-invasive prenatal DNA screening (NIPS) for chromosomal pathologies. Study Design: cross-sectional study. Materials and Methods. We have examined two groups of pregnant women: group I included 49 patients with constantly low foetal DNA (twice lower than 4%) selected out of 1,505 women examined at Kulakov National Medical Scientific Centre of Obstetrics, Gynaecology and Perinatal Medicine of the Ministry of Health of Russia during the last 2 years. 17 women were administered LMH and 32 women did not receive it. Group II included 113 pregnant women with a normal foetal DNA fraction (at least 4%), that were selected randomly out of patients who were examined during the same period. 56 pregnant women were administered LMH and 57 were not. Next Generation Sequencing was used as an NIPS method. In order to determine the foetal DNA level, we amplified DNA loci with single nucleotide polymorphisms. Study Results. In group I (low foetal DNA fraction), where no LMH therapy was initiated, median values were 3.5% (3.2–3.8%); if LMH was administered, these values made 3.6% (3.4–3.9), while in group II — 7.7% (6.1–9.5%) and 7.9% (6.0–10.5%), respectively; no significant differences (p = 0.29 and p = 0.7, respectively) were recorded in both cases. Conclusion. Use of LMH does not affect NIPS; therefore, it is not necessary to adjust the LMH therapy in pregnant women prior to NIPS. Keywords: non-invasive prenatal DNA screening, heparin, anticoagulants, low molecular heparins, habitual abortion, pregnancy complications.

Introduced into clinical practice in 2011, non-invasive prenatal testing (NIPT) allows detection of chromosomal aneuploidies in the fetus using maternal blood samples. Multiple studies have shown that one of the key factors affecting the result of this test is the fetal DNA fraction. The aim of this work was to develop a method capable of measuring the fetal DNA fraction based on targeted SNP sequencing. We selected polymorphisms with high frequency of heterozygous genotype from the international HapMap database. To estimate the frequency of these polymorphisms in the Russian population, we used 827 DNA donor samples. Fetal DNA fraction was measured in 87 plasma samples of pregnant women. Sequencing was performed on Ion Proton and Ion S5. We determined the frequencies of the studied polymorphisms in the pooled samples and compared the data on 53 SNPs in the pooled and 87 individual samples. The median difference was 3.4%. The correlation between the results obtained by targeted SNP sequencing and Y chromosome read count was 0.7. Thus, the proposed method can be used to estimate the fetal DNA fraction using SNP genotyping regardless of the fetus's sex.

Неинвазивный пренатальный ДНК-скрининг (НИПС) анеуплоидий по крови матери применяется для выявления хромосомных анеуплоидий (ХА) с 2011 г.Многочисленные клинические исследования показали, что важным параметром при проведении