Preplanned Studies: Trends in the Prevalence of Births with Chromosomal Abnormalities — Haidian District, Beijing Municipality, China, 2013–2022

Data derived from a hospital-based birth-defect surveillance system in Haidian District, Beijing indicates a steady rise in the prevalence of CAs over the past decade. The data further reveals a significant increase in the prevalence of most CAs subtypes from 2013 to 2022. Interestingly, the year 2015 marked a major turning point in this trend wherein the prevalence growth rate significantly escalated post-2015.

Globally, CAs occur in approximately 4 to 9 out of every thousand newborns (6). In the Haidian District of Beijing, the prevalence of CAs is relatively low, with 4.595 per thousand. It is important to mention, however, that this prevalence has seen a steady increase, reaching 8.274 per thousand in 2022. Due to regional differences in detection rates and capabilities, it would be inaccurate to directly compare the prevalence of CAs between different regions. Nonetheless, a similar increasing trend in prevalence, as seen in this study, has been reported in several prior studies. For instance, the prevalence of trisomy 21, trisomy 18, and trisomy 13 syndromes in Europe showed an escalation between 2005 and 2021 (3). In Zhejiang Province, the overall prevalence of CAs rose from 1.209 per thousand to 3.922 per thousand between 2014 and 2020, with varying degrees of increase in the prevalence of trisomy 21 syndrome, SCAs, and microdeletions/microduplications (4). Similarly, in Guangdong Province, the prevalence of trisomy 21 syndrome surged from 0.465 per thousand to 1.364 per thousand between 2011 and 2018 (7).

In our investigation, it was observed that the maternal age for children suffering from CAs during the period 2016–2022 was statistically higher compared to 2013–2015. This change coincided with China’s transition from a one-child to a universal two-child policy in 2016. As a result, there was a noticeable increase in the percentage of pregnancies associated with older mothers, multiple pregnancies, and multiparous women from 2016 to 2022 in contrast to the numbers recorded between 2013 and 2015. Earlier research determined that advanced maternal age significantly raises the risk for CAs (8). Consequently, it can be posited that the shift in birth policy may have indirectly increased maternal age, gravidity, and parity, thereby causing a surge in the prevalence of CAs post-2016 (9).

Conversely, the observed surge in reported cases of CAs might represent advancements in prenatal diagnostic methods in Haidian District and increased awareness among expectant mothers. The National Health Commission of the People’s Republic of China initiated a nationwide pilot program for this technology in 2016 and the NIPT technology was applied in 2017 in Beijing (10). Evidently, NIPT technology exhibits high performance in early detection of CAs, managing to identify certain variants of CAs that proved challenging via traditional methods. Owing to its elevated sensitivity, the prevalence of missed diagnosis prior to pregnancy is minimized, which may partially account for the rising prevalence of CAs noted in this study.

The NIPT not only enhances the efficacy of detection for autosomal trisomies, but also proves useful in identifying certain types of SCAs, such as 47 XYY and 47 XXY, and other CAs (4). Ethical considerations necessitate that any decision to proceed with therapeutic abortion for CAs must fully respect the patient’s wishes. Therefore, healthcare practitioners need to deliver individualized and detailed genetic counseling based on the detection information. For severe cases like trisomy 21 syndrome, healthcare practitioners may provide conclusive advice allowing the patient to consider therapeutic abortion before the 28 weeks gestation mark. However, certain CAs such as some SCAs subtypes and structural CAs are neither fatal nor severely debilitating. Here, practitioners’ advice should take into account a variety of factors such as prognosis, the patient’s physical condition, and financial capabilities. The final decision rests with the patient whether to proceed with abortion or explore different interventions. Limited counselling or insufficient explanation can lead to unnecessary abortions resulting in unwarranted intervention. The exemplary detection capacity of NIPT has led to an uptick in the proportion of hitherto rare SCAs and other CAs, posing fresh challenges for genetic counselling and healthcare practitioners.

Our findings indicate that the SCA abortion rate did not considerably rise post-2016, an encouraging sign. However, it is crucial to note that the abortion rate for microdeletion/microduplication was higher between 2016–2022 compared to 2013–2015. Looking ahead, the focus must be on increasing awareness and education among expectant women for a proper understanding. Healthcare practitioners must also strive for accurate interpretation and evaluation of test information, to aid patients in making appropriate treatment decisions in light of the varying prognoses associated with CAs.

The present study possesses several notable strengths. Primarily, Haidian District boasts a 100% rate of hospital-based delivery, making the district’s hospital surveillance data an accurate representation of the population. Secondary strength lies in the district’s high level of medical care, coupled with the established diagnostic proficiency of affiliated midwifery organizations. The deployed surveillance system, with its extensive review and rejection mechanisms for diagnostic results, bolsters data reliability at both the district and municipal levels. Moreover, the classification of CAs within the surveillance system — trisomy 21, trisomy 18, trisomy 13 syndrome, SCAs, and other CAs — was subdivided into more precise subtypes. This allows for a more nuanced analysis of CAs prevalence and also aids in enhancing future classification systems.

This study encompasses several limitations. Primarily, as a regional observational research, the findings are specifically indicative of the urban region in Beijing and may not be comprehensively representative of either the complete Beijing populace, or China overall. Additionally, the study did not incorporate an exhaustive categorization of structural CAs. Lastly, certain data categories such as specific exposure factors were omitted from collection in this research, limiting the study’s scope to merely detailing the distribution of CAs rather than identifying potential risk factors.

The prevalence of CAs in Haidian, Beijing, has markedly risen from 2013 to 2022. This increase may be ostensibly linked to a rise in advanced maternal age and the utilization of NIPT. Heightened detection rates of CAs can expedite treatment for pregnant women diagnosed with poor prognosis conditions such as trisomy 21 syndrome, thus alleviating their burden. Conversely, attention must also be accorded to other CAs, such as SCAs, and women should be educated to form an accurate comprehension of these conditions. Achieving this requires healthcare practitioners to possess a comprehensive understanding of the advantages and disadvantages of prenatal diagnostic methods, patient preferences, and ethical evaluations.

No conflicts of interest.

All the participants in this study. The authors also thank all the obstetricians and pediatricians in the hospital-based birth-defect surveillance system for their great effort in data collection.