Characteristics of first trimester miscarriages assesed by chromosomal analysis of products of conception with next generation sequencing

Abstract

Chromosomal abnormalities are the major cause of early pregnancy loss. Chromosome testing of products of conception (POC) provides valuable information for counseling and clinical managing of patients. We previously showed that next generation sequencing (NGS) can be utilized as a technique demanding lesser specimen with a lower failure rate, higher resolution, and shorter turnaround time than conventional karyotyping which is requiring labor-intensive and time-consuming cell culture with possible maternal cell contamination. We aimed to assess the efficacy of NGS method for chromosomal analysis of POC. In addition, we attempted to identify any associations between the incidence of chromosomal abnormalities and the profile of patients as well as fetal development in an assisted reproductive technology (ART) program. Retrospective study with a single reference genetic laboratory. Total of 131 consenting patients with first trimester miscarriages after vitrified-warmed embryo transfer were involved. POC samples were obtained bydilation and curettage between 7 to 10 gestational weeks. Chorionic villi were isolated under a dissecting microscopy, subsequently processed for NGS chromosomal analysis. Incidence of each chromosomal abnormality was reported and evaluated according to the patient profile, such as maternal age, previous history of miscarriage and fetal development. Finally, frequency of mosaics was also assessed. After NGS analysis, 28 cases (21.4%) were found to be normal, and the remaining 103 (78.6%) were abnormal, including 10 (7.6%) mosaics. Among normal karyotypes, ratio of female to male was 1.15 (15/13). Trisomies were the most common abnormalities except for the chromosome X monosomy (10.7%). Aneuploidy of chromosome 22 (20/113, 17.7%), 15 (16/113, 14.2%), 16 (16/113, 14.2%), X (13/113, 11.5%) and 21 (11/113, 9.7%) including overlaps, were most frequently involved. Mean maternal age of chromosomally abnormal cases was significantly higher than that of normal karyotypes (39.0 ± 18.5 vs 36.9 ± 16.5 years, P<0.05). Patients with more than equal 3 previous miscarriages showed a significantly lower rate of abnormalities than those with <3 miscarriages (28.6% vs 81.5%, P<0.01). Rate of abnormalities with positive fetal cardiac activity was not different from that of anembryonic pregnancies (80.0% vs 76.1%), although fetal cardiac activity was detected in all the 45,XO cases. Interestingly, however, mosaic abnormalities were significantly more often detected in anembryonic pregnancies than the other (15.2% vs 3.5%, P<0.05). With more conclusive and accurate results and higher resolution by NGS, we were able to characterize early pregnancy loss after ART, demonstrating relatively high rate of abnormalities with gender ratio being close to 1. Patients with repeated pregnancy loss showed lower chromosomal abnormalities indicating other causes for miscarriages in this group of patients. A higher incidence of mosaics detected in anembryonic pregnancies warrants further investigation.