Preplanned Studies: Analyzing the Trends and Causes of Birth Defects — Jinan City, Shandong Province, China, 2005–2022

Birth defects (BDs) are a collection of structural, functional, and/or biochemical-molecular anomalies identifiable at birth (1). With advancements in economic and social sectors, mortality rates from infections and malnutrition among children and adolescents have significantly decreased. However, there’s a rising trend in deaths due to BDs (2). Current estimates suggest that BD prevalence is 4.7% in developed countries, 5.6% in middle-income countries, and 6.4% in low-income countries (3). Moreover, disabilities and cancer arising from birth defects pose growing threats to children’s health (4). Given these developments, BDs have become a critical global health concern demanding urgent attention.

In this context, China has also seen a rise in the significance of BDs in public health. According to the 2012 “Birth Defect Prevention Report” published by the Ministry of Health, China’s prevalence rate was 5.6 per 10,000 births in 2011 (5). Notably, 19.1% of infant deaths were attributable to BDs, and BDs were the root cause of 9.6% of disabilities. Furthermore, BDs were established as the second leading cause of infant death in China (6). Given its status as a developing nation with a large population, it is critical for China to reduce the incidence rates of birth defects.

Many Chinese studies have reported on the prevalence of BDs. Current protocols mandate reporting prenatal abnormalities in body structure, function, or metabolism. The extensive use of ultrasound technology in obstetrics has led to an increase in the detection of BDs prior to 28 weeks of gestation. Consequently, there is a compelling need to extend the surveillance period for birth defects.

In Jinan, most expectant mothers typically initiate hospital visits around the 12th week of gestation to secure a maternal record and undergo a medical examination. Therefore, starting birth defect monitoring from this gestational stage is both methodologically robust and practically feasible. As a result, a birth defect monitoring network was established across all district and county levels in Jinan in 2005. Accordingly, a birth defect monitoring network encompassing all district and county levels throughout Jinan was established in 2005. Health centers at the township level and county-level hospitals providing midwifery services were required to report relevant birth defect data. In 2011, the reach of this network was expanded to include all medical institutions offering pregnancy health and midwifery services. Additionally, an information system designed to collect precise birth defect data was implemented in the same year. All information relating to mothers and newborns, inclusive of data on birth defects, was submitted via an online reporting system, enabling accurate and reliable data.

Between 2005 and 2008, BDs were identified from the 28th week of gestation until 7 days post-birth. However, from 2008 to 2022, the period for determining BDs broadened to begin at 12 weeks gestation and extended through to 7 days after birth. Our study holds the potential to inform governmental policy-making with scientifically-based recommendations and serve as a template for developing cities to prevent BDs.

Data was aggregated from registry forms and an electronic information system. Between 2005 and 2015, paper forms were utilized for data collection. However, during 2015–2022, data compilation transitioned to an electronic information system. The collected data encompassed a range of factors such as the total number of births, maternal age, residency location (either urban or rural), and neonate gender. We accounted for 1,463,842 births and 28,537 BDs within our study.

Both external malformations and chromosomal aberrations, encompassed under BDs, were diagnosed under the International Classification of Diseases (10th edition).

To maintain data accuracy, standardized procedures were established for data handling, abstraction, and evaluation. Hospital surveillance teams verified diagnoses, reviewed data, and checked medical records following these standards. Annual surveys revealed a 0.5% underreporting rate of birth defects in Jinan. Missing reports were documented yearly.

The Cochran-Armitage test (CAT) was used to analyze the trends of BD prevalence. Differences in BDs were tested using the Chi-square test. All statistical analyses were executed using SPSS software (version 18.0: IBM Corp., Armonk, NY, USA), with a significance level of P<0.05.

Between 2005 and 2022, there were 1,463,842 recorded births and 28,537 instances of BDs, yielding a prevalence of 194.93 per 10,000 births. Time trend analysis illustrated a rise in BD rates from 99.15 per 10,000 births in 2005 to 290.27 per 10,000 births in 2022. This represents an aggregate increase of 191.21% and an annual increase of 10.70% (P<0.05). The peak birth defect prevalence was in 2022, at 290.27 per 10,000 births. A significant increase inflection point was identified in 2016, with prevalences exceeding 230 per 10,000 births from then on.

During the study period, urban areas had a BD rate of 234.54 per 10,000 births, while rural areas had 161.40 per 10,000 births. The prevalence in urban areas significantly surpassed that in rural areas, averaging 31.17% (P<0.05). A time trend analysis indicated an increase in the incidence of BDs in both urban and rural areas, with the average annual growth rate in rural environments being faster than in urban ones (13.63% vs. 7.85%) (Table 1 and Figure 1).

Figure 1. 

The prevalence of birth defects between urban areas and rural areas from 2005 to 2020.

Note: Two distinct periods were demarcated based on changes in population policies: 2005–2016, preceding the implementation of the universal two-child policy; and 2017–2022 following the implementation of the universal two-child policy.

Abbreviation: BD=birth defect.

Throughout our study, we observed a significantly higher prevalence of BDs in two specified age groups. Mothers under 20 had a BD rate of 272.91 per 10,000 births, and those over 35 had 236.09 per 10,000 births. These age groups showed significantly higher BD incidences compared to other groups (P<0.05).

From 2005 to 2022, the proportion of pregnant women under 20 surged by 2037.50%, while those over 35 increased by 66.35% (Table 2).

From 2005 to 2022, the top 5 BDs were congenital heart disease (88.54 per 10,000 births), polydactyly (19.23 per 10,000 births), cleft lip and/or palate (10.41 per 10,000 births), hypospadias (9.84 per 10,000 births), and syndactyly (5.35 per 10,000 births).

Of the 10 major BDs analyzed, 7 showed an upward trend, and 3 declined from 2005 to 2022 (P<0.05). Congenital heart disease exhibited a significant increase at 867.36%, reflecting an average annual growth of 48.19%. The occurrence of Down syndrome similarly increased by 299.14%, with an average annual increase of 16.62%. Polydactyly also rose by 223.09%, averaging an annual increase of 12.39%. On the other hand, Neural Tube Defects demonstrated a stark decrease at 90.35%, with an average annual decline of 5.02%. The rates of Congenital Hydrocephalus similarly fell by 63.81%, with an average annual decrease of 3.54%. Limb Shortening also declined by 53.19%, averaging an annual decrease of 2.96%. (Table 3 and Figure 2).

Figure 2. 

The prevalence of (A) congenital heart disease, (B) polydactyly, (C) Down’s syndrome, (D) neural tube defects, (E) congenital hydrocephalus, and (F) limb shortening from 2005 to 2020.

Abbreviation: BD=birth defect.