Objective:

To systematically evaluate the primary influencing factors of birth defects in China from 2019 to 2025.

Approach:

• Literature Search: A comprehensive search was conducted in various databases for literature published from January 2019 to December 2025.
• Data Analysis: Two researchers independently performed literature screening, quality assessment, and data extraction. Meta-analysis was conducted using Stata 17.0 software.
• Subgroup Analysis: Subgroup analyses were carried out based on types of birth defects, study regions, or study quality for factors with high heterogeneity.

Key Findings:

• Seventeen influencing factors of birth defects were identified.
• Maternal age ≥35 years (OR = 1.26, 95% CI: 1.05–1.47), maternal BMI > 30 kg/m2 (OR = 1.42, 95% CI: 1.25–1.58), and maternal drug use (OR = 1.06, 95% CI: 0.58–1.54) were significant maternal factors.
• Healthcare service factors included low rates of premarital examinations (OR = 0.36, 95% CI: 0.30–0.43) and pregnancy examinations (OR = 0.41, 95% CI: 0.21–0.62).
• Nutritional factors such as irregular folic acid supplementation (OR = 1.32, 95% CI: 0.09–2.55) were linked to higher risks of neural tube defects (OR = 2.34, 95% CI: 2.01–2.72).
• Income <5,000 yuan (OR = 1.41, 95% CI: 0.90–1.93) and preterm birth (OR = 1.07, 95% CI: 0.04–2.10) were also identified as significant risk factors.

Interpretation:

Limitations:

• The majority of studies included were either single-center or region-specific with small sample sizes.
• Previous meta-analyses did not account for the period following major policy changes.
• Few systematic reviews conducted subgroup analyses based on specific types of birth defects.

Conclusion:

Numerous factors influence the occurrence of birth defects.