Single-gene recessive diseases include autosomal recessive and X-linked recessive genetic diseases, which usually have no family genetic history and cannot be detected in routine prenatal examination; these diseases are discovered after birth when symptoms slowly appear. Recessive genetic diseases easily cause blindness, deafness, body deformities, intellectual disability, growth retardation, the dysfunction or failure of tissues and organs, and even serious harm, such as death, which brings a heavy burden to families and society. In 2011, for the first time, Bell et al. [18] used next-generation sequencing technology to screen 104 subjects for 448 recessive genetic diseases and found that each person carried 2.8 pathogenic mutation genes, highlighting the need for ECS in the population. ECS provides screening for a variety of autosomal recessive and X-linked genetic diseases. With the widespread development of carrier screening and the development of gene testing technology, the reproductive decision-making of couples can be better guided, and the risk of serious single-gene diseases in offspring can be effectively reduced [19]. Therefore, capillary electrophoresis, a first-generation sequencing technology, was used in this study to screen for single-gene disease carriers in the population of childbearing age with normal phenotypes in Anhui Province, which is conducive to providing timely intervention measures for high-risk couples before pregnancy or in early pregnancy and reducing birth defects.

The total carrier rate of pathogenic gene variations in the population screened was 20.31% in this study, indicating the need for carrier screening. Lazarin et al. [20] conducted panethnic carrier screening for 108 diseases, and the total carrier rate was 24%. Zhao et al. [13] performed carrier screening for 11 diseases in a Chinese multiethnic population, with a total carrier rate of 27.49%. The possible reasons for the differences in the results are related to the differences in the regions of the studied populations, sample sizes, types of diseases screened, and sequencing technology used. Among the 65 carriers detected, 2 carried two different mutations of the ATP7B gene, namely, ATP7B: c.588C > A (p.D196E) and ATP7B: c.3316G > A (p.V1106I). Because the phenotypes of the subjects were normal, according to the literature [21], the c.588C > A mutation of ATP7B is usually linked with the c.3316G > A mutation. In this state, it was estimated that the tested person was a carrier of hepatolenticular degeneration. The top three pathogenic genes in this study were GJB2, ATP7B, and SLC26A4; 14 GJB2 carriers were detected, and the most common mutation site was c.235delC (p.L79Cfs*3). A total of 12 SLC26A4 carriers were detected, and the most common mutation site was c.919-2A > G; a total of 13 ATP7B carriers were detected, and the most common mutations were c.2333G > T (p.R778L) and c.3316G > A (p.V1106I). The common mutation spectrum of GJB2 and SLC26A4 in this study was consistent with previous literature reports of the Chinese population [22, 23], while the mutation spectrum of ATP7B was inconsistent with a research report of Chinese patients with Wilson's disease [24]. In addition, we identified a male premutation carrier of Fragile X syndrome. The CGG repeats of male premutation carriers are not expanded when they are transmitted to the next generation, so male premutation carriers generally do not have an increased risk of fetal disease. However, if a daughter is born, she will be a premutation carrier, and genetic counseling is recommended [25, 26]. Among the 84 couples, 1 (1.19%) was found to be a high-risk couple, with both partners being carriers of type 1A (GJB2 gene) autosomal recessive deafness, and their risk of giving birth to deaf children was 25%. For high-risk couples, genetic counseling is needed to help the partners choose prenatal diagnosis or delivery management to improve clinical outcomes. The Chinese population has a high carrier rate of the deafness gene. A multicenter study by Cai on genetic screening for hereditary deafness among newborns in Zhejiang Province, China showed that 8.71% of newborns carried at least one hereditary deafness-related variant [27]. The carrying rate of hereditary deafness in this study was 8.13%. Therefore, genetic deafness diseases were included for screening in this study, and high-risk childbearing couples were identified. Genetic disease screening, which is conducive to early detection and diagnosis, can effectively avoid the occurrence of deafness and birth defects and allows early intervention for newborns, which is conducive to improving language development.

With the development of sequencing technology, next-generation sequencing (NGS) has been widely used in carrier screening for single-gene diseases with the advantages of high throughput and low cost [28]. However, NGS technology still has limitations in genetic screening for single-gene diseases. First, it cannot detect some special gene mutations with a high incidence of genetic diseases (such as pseudogenes, inversions, and CGG repeat mutations). Second, positive NGS test results still need to be verified by generation sequencing. In addition, the most important thing is that NGS technology has a high probability of detecting mutations of unknown clinical significance, and it is difficult for laboratories to interpret these test results in an accurate and detailed way, causing great confusion and burdens for clinicians and patients [28]. Therefore, in this study, carrier screening was performed by capillary electrophoresis-based multiple PCR analysis, which could screen for some special high incidence genetic diseases that could not be detected by NGS, including congenital adrenal hyperplasia (CAH), spinal muscular atrophy (SMA), and Fragile X syndrome. In this study, the carrier rates of CAH and SMA were 2.81% and 2.50%, respectively, suggesting that screening for these two diseases is warranted.

However, this study also has some limitations. First, a limited number of definite pathogenic sites were included, and pathogenic mutations and emerging variants outside the detection range could not be identified, which may increase residual risks. The pretest and posttest consultations to inform the subjects of the benefits and limitations of this study needs to be emphasized. Second, we observed 8 out of the 15 genetic diseases in the study population, which may be related to the small sample size and the types of diseases screened. We will include more subjects for screening in the future. Third, due to time constraints and insufficient follow-up, the follow-up of pregnancy outcomes and newborns will be carried out in the future. Finally, the results of this study were not evaluated by NGS. In the future, we will continue to conduct in-depth research to compare the results of ECS in this study with those of NGS and explore the consistency of the two methods in estimating overlapping genetic variants.