Open access Protocol BMJ Open: first published as 10.1136/bmjopen-2021-053617 on 27 August 2021. Downloaded from Comprehensive non- invasive prenatal screening for pregnancies with elevated risks of genetic disorders: protocol for a prospective, multicentre study Chenming Xu,1 Xiaoqiang Cai,2 Songchang Chen,1 Qiong Luo,3 Hui Xi,4 Dan Zhang ,5 Hua Wang,4 Yanting Wu ,1 He- Feng Huang,1,3 Jinglan Zhang 1,2 To cite: Xu C, Cai X, Chen S, ABSTRACT Strengths and limitations of this study et al. Comprehensive non- Introduction Chromosomal abnormalities and monogenic invasive prenatal screening disorders account for ~15%–25% of recognisable birth ► This is the first prospective, multicentre clini- for pregnancies with elevated defects. With limited treatment options, preconception risks of genetic disorders: cal study for an integrated non- invasive prenatal and prenatal screening were developed to reduce the protocol for a prospective, screening test for both chromosomal abnormalities incidence of such disorders. Currently, non- invasive multicentre study. BMJ Open and monogenic diseases. prenatal screening (NIPS) for common aneuploidies is 2021;11:e053617. doi:10.1136/ ► This study is focused on a panel of preselected dis- implemented worldwide with superiority over conventional bmjopen-2021-053617 eases which have relatively high incidence. serum or sonographic screening approaches. However, the ► The limitation for this study includes population ► Prepublication history and clinical validity for the screening of frequent chromosome additional supplemental material stratification for high- risk pregnancies and potential segmental copy number variations and monogenic for this paper are available loss of postnatal follow- up. online. To view these files, disorders still awaits to be proved. please visit the journal online Methods and analysis This study is a multicentre, (http:// dx. doi. org/ 10. 1136/ prospective study. The participants were recruited from 2 bmjopen- 2021- 053617). three tertiary hospitals in China starting from 10 April defect worldwide. Although the causes of 2021. The study is expected to conclude before 10 most cases are unknown, about 15%–25% of CX, XC and SC contributed October 2022. Pregnant women with abnormal prenatal birth defects are due to genetic diseases such equally. screening results indicated for invasive prenatal diagnosis as chromosomal abnormalities and mono- http://bmjopen.bmj.com/ or those who decide to terminate their pregnancies due 3 Received 19 May 2021 genic disorders. Accepted 13 August 2021 to abnormal ultrasound findings will be evaluated for enrolment. Cell- free DNA extracted from the maternal The screening of severe genetic diseases plasma will be used for an analytically validated Great efforts have been made to prevent birth comprehensive NIPS test developed by Beijing BioBiggen defects with an underlying genetic aetiology. Technology Co. (Beijing, China). The diagnostic results from Carrier screening for recessive disorders such prenatal or postnatal specimens as well as the pregnancy as Tay- Sachs disease was proved to be highly outcome data will be collected to examine the clinical effective for the reduction of its incidence.4 sensitivity, specificity, positive and negative predictive on October 1, 2021 by guest. Protected copyright. values of the test. The first- trimester combined screening for Ethics and dissemination This study was approved by fetal aneuploidies by prenatal ultrasound the Obstetrics and Gynecology Hospital of Fudan University and maternal serum biochemical testing (2020-178). Results of this study will be disseminated to detects over 85% common trisomies at a public through scientific conferences and a peer- reviewed false- positive rate of ~5% which can lead to © Author(s) (or their journal. Written informed consents will be obtained from parental anxiety and excessive invasive diag- employer(s)) 2021. Re- use participants. nostic procedures for otherwise normal preg- permitted under CC BY-NC. No Trial registration number ChiCTR2100045739. nancies imposing a risk for pregnancy loss.5 6 commercial re- use. See rights and permissions. Published by Since the discovery of circulating fetal cfDNA BMJ. in the maternal plasma during pregnancy, its For numbered affiliations see INTRODUCTION biological characteristics and clinical impli- 7 8 end of article. Genetic aetiology of birth defects cation have been extensively studied. Non- Birth defects are congenital conditions invasive evaluation for fetal gender and risks Correspondence to causing structural or functional anomalies for monogenic disorders, aneuploidies, and Dr Jinglan Zhang; jinglanzhang@ foxmail. com and at birth, which greatly contribute to infant chromosome segmental CNVs were devel- 1 Dr He- Feng Huang; mortality and disability. Approximately oped using different molecular or genomic huanghefg@ hotmail. com 3%–5% of newborns are affected by a birth techniques.9–11 Importantly, the emergence Xu C, et al. BMJ Open 2021;11:e053617. doi:10.1136/bmjopen-2021-053617 1 Open access BMJ Open: first published as 10.1136/bmjopen-2021-053617 on 27 August 2021. Downloaded from of next- generation sequencing (NGS) technology Accurate genetic counselling is critical to the success of enabled a practical population-based screening method a prenatal screening test which should provide informa- for Down syndrome.12 13 In the past decade, NGS- based tion regarding disease characteristics, natural history, non- invasive prenatal screening (NIPS) for trisomy 21, 18 penetrance, expressivity, genotype- phenotype correla- and 13 has become a new standard for prenatal care with tion, etc. The benefits and risks of NIPS- M need to be 14 proven clinical validity. Recently, NIPS was used to detect carefully evaluated when patients are counselled based rare autosome trisomies, sex chromosome aneuploidies, on current understanding of the diseases.24 15 16 and microdeletion or microduplication syndromes. This study is aimed to address above important issues However, monogenic disorders which represent another with a focus on the clinical validation of an innovative major cause of birth defects are beyond the scope of the NIPS for concurrent screening of common aneuploidies, current screening of chromosomal abnormalities, and CNVs and monogenic disorders. The potential bene- the clinical validity for the screening of such diseases are fits and the limitations of this screening test will also be yet to be demonstrated. explored based on the pregnancy outcome data. The development of NIPS for monogenic disorders Previous studies have shown that the analysis of fetal Aims cfDNA was useful to determine the inheritance of 1. To assess the clinical validity of a novel NIPS test for parental alleles associated with autosomal or sex- linked concurrent screening of seven common aneuploid- recessive monogenic diseases.17 18 Additionally, non- ies, nine microdeletion and microduplication syn- invasive prenatal testing was also accurate for the diag- dromes (MMS) and 155 monogenic disorders (75 nosis or screening of the de novo or paternally inherited genes). variants causing dominant diseases such as achon- 2. To evaluate the pregnancy outcome for the partici- droplasia and Noonan spectrum disorders.19 20 These pants of this comprehensive NIPS. studies showed potential clinical utility for monogenic NIPS (NIPS- M) in pregnancies at moderate risks (eg, METHODS AND ANALYSIS pregnancies with advanced paternal age or ultrasound Study design soft markers). These tests could also be used for the This prospective cohort study aims to evaluate how a screening of diseases which can only be discovered at late gestational ages (eg, skeletal disorders). Although comprehensive NIPS test will reveal pregnancies at risks the analytical accuracy of NIPS- M has been well demon- for both chromosomal and monogenic disorders. It is strated, such tests will not be widely accepted without a prospective, multicentre study focused on pregnant further evidence- based clinical study.21 First, the clin- women with indications for prenatal diagnosis, including ical validity of NIPS-M has not been supported by large fetal ultrasound markers, high risk results by maternal prospective studies. The follow- up studies of the preg- serum screening or routine aneuploidy NIPS. Pregnancies http://bmjopen.bmj.com/ nancies tested positive or negative should be evaluated with elective abortion due to fetal structural abnormality by clinical examination or golden standard diagnostic will also be recruited. To assess the performance metrics tests. Additionally, although isolated cases have demon- of this NIPS test, cases will be followed up to compare strated the benefits of NIPS- M leading to early diagnosis the screening results with the prenatal or postnatal diag- and better prenatal/postnatal management, the bene- nostic test results including sequencing, chromosomal fits for the management of patients with different indi- CNV testing and/or karyotyping. Clinical follow-up will cations are yet to be explored by larger studies.20 22 23 be pursued regarding the pregnancy outcome up to 6 Third, the limitations of NIPS- M need to be evaluated. weeks after birth (figure 1). on October 1, 2021 by guest. Protected copyright. Figure 1 The diagram for the clinical validation of a comprehensive non- invasive prenatal screening test. 2 Xu C, et al. BMJ Open 2021;11:e053617. doi:10.1136/bmjopen-2021-053617 Open access BMJ Open: first published as 10.1136/bmjopen-2021-053617 on 27