This study presents a comprehensive analysis of birth defect prevalence trends in China from 2007 to 2021. By analyzing a nationwide population-based dataset, we identified significant upward or downward trends for various birth defects and revealed epidemiological patterns of major conditions.

Compared with previous data from the Chinese Birth Defects Monitoring Network (CBDMN), the prevalence of selected birth defects in our findings is marginally lower than reported by hospital-based surveillance data [16]. In alignment with the findings of a recent meta-analysis, our study confirms CHDs, polydactyly, and CL/P as leading birth defects. However, we observed significantly higher rates of CHDs and polydactyly, while CL/P prevalence was lower. Notably, NTDs were considerably less frequent in our study (1.9%) compared to Kang et al.’s (12.8%) [17]. Global prevalence rate comparisons are complex due to multiple factors, including differences in ethnicity, socioeconomic status, environmental exposures, and variations in surveillance practices such as diagnostic criteria and study design. In our data, the prevalence of conditions such as anencephaly, LRD, CP, anorectal atresia/stenosis, and hypospadias aligns with that observed in Japan [18]. The prevalence rates of anotia/microtia and CL/P are comparable to those in South Korea [19], but the rates of NTDs, CP, anorectal atresia/stenosis, and CHDs are significantly lower. Conversely, our data show a higher prevalence of anotia/microtia compared to Germany [16], while the rates of NTDs, CL/P, and Down syndrome are substantially lower. Notably, the prevalence of Down syndrome is considerably lower than in the United States and some European countries [3, 18, 20].

Downward trends were observed for NTDs, hydrocephalus, CL/P, LRD, omphalocele, Down syndrome, and TOF during the study period. The decline in central nervous system defects can largely be attributed to national initiatives, such as promoting folic acid supplementation for women of reproductive age [21,22,23]. In addition, the reduced prevalence of Down syndrome and omphalocele is likely due to the impact of advanced prenatal screening and diagnostic technologies, enabling earlier detection and possible termination of affected pregnancies prior to 28 weeks of gestation [3, 7, 24,25,26,27].

In contrast, upward trends were observed for hypospadias, CP, microtia/anotia, polydactyly, syndactyly, VSD, ASD/PFO, and PDA. The increasing prevalence of VSD, ASD/PFO, and PDA likely reflects improvements in diagnostic practices, disease screening, and the routine use of echocardiography, which has facilitated the detection of mild or asymptomatic CHDs during the perinatal period [16, 20]. Additionally, as noted in previous studies, environmental changes may be associated with the incidence of hypospadias [28,29,30].

Geographical disparities in the prevalence of certain defects are evident, with higher prevalence rates of NTDs and CL/P observed in rural and western regions. These disparities may stem from limited access to folic acid supplementation and inadequate maternal nutrition, especially in rural areas where folic acid-fortified foods and prenatal vitamins are less accessible. Moreover, rural populations may experience greater exposure to pesticides, heavy metals, and pollutants, which could impact the prevalence of these anomalies [31,32,33,34]. Discrepancies in prenatal diagnosis rates may also contribute, as urban women generally have better access to prenatal screening and diagnosis, potentially leading to more terminations of pregnancies affected by NTDs or CL/P. The higher prevalence of CP, hypospadias, polydactyly, Down syndrome, and CHDs in urban and eastern regions may be related not only to the extensive implementation of prenatal screening and diagnosis but also to factors such as increasing older maternal age (Supplementary Fig. 1), increased air pollution [35,36,37], chemical exposure, and distinct climatic conditions [38, 39]. Further research is essential to clarify the intricate relationships and mechanisms driving these regional variations in birth defects prevalence.

Maternal age significantly influences the prevalence of birth defects, with younger mothers more prone to conditions like NTDs, hydrocephalus, CL/P, clubfoot, polydactyly, syndactyly, omphalocele, and gastroschisis [40,41,42]. Conversely, older mothers exhibit higher rates of CP, hypospadias, Down syndrome, and CHDs. The increased risks associated with teenage pregnancies could be attributed to factors such as underdeveloped growth, physiological immaturity, poorer nutrition, unhealthy lifestyles, lower rates of prenatal screening, and psychosocial stress [43, 44]. For older mothers, the increased likelihood of chromosomal abnormalities and comorbidities, such as diabetes and hypertension, could lead to abnormal fetal cardiovascular development and higher CHD risk [20]. These observations highlight the necessity for age-specific interventions to support maternal health. Additionally, the higher prevalence of microtia/anotia, polydactyly, and syndactyly in male infants is consistent with findings from previous research [8, 16, 45]. The biological and epidemiological mechanisms underlying these trends remain largely unclear and require further research.

This study, while comprehensive, has certain limitations. Firstly, it focuses exclusively on perinatal defects identified at or after 28 weeks of gestation, omitting insights into pregnancy losses or induced abortions before the 28th week. As a result, a definitive understanding of the specific reasons behind observed decreases in incidence rates remains at a speculative level. Secondly, the absence of detailed clinical data precludes a thorough analysis of risk factors such as diabetes, hypertension, smoking, alcohol consumption, and nutritional status. Thirdly, due to the system's coding conventions, certain defects such as ASD and PFO are indistinguishable, precluding more granular analysis and comparison. Despite these limitations, the strength of this study lies in its substantial nationwide population-based sample, which includes over 5 million births and 100,000 infants with birth defects over a 15-year period. This large sample size offers valuable insights into overall trends. Future investigations with more detailed maternal and fetal data could further clarify the underlying mechanisms behind these observed patterns.

In summary, this extensive nationwide population-based study has delineated varied temporal trends in the prevalence of major birth defects in China from 2007 to 2021. A decrease in the prevalence of NTDs, hydrocephalus, CL/P, LRD, omphalocele, Down syndrome, and TOF was observed. In contrast, there was an increase in the prevalence of conditions such as microtia/anotia, hypospadias, polydactyly, syndactyly, and certain types of CHDs. Additionally, the study highlighted significant geographical disparities and maternal age-specific prevalence patterns of certain defects. These findings offer valuable insights into the epidemiological trends and distributions of birth defects, which can inform strategic prevention initiatives and direct future research endeavors aimed at alleviating the impact of birth defects in China.