The Impact of Pregnancy Termination before 28 Weeks of Gestation on the Overall Prevalence of Birth Defects - Shaanxi Province, China, 2014-2020.

Introduction: The prevalence of birth defects (BDs) at ≥28 gestational weeks in China has declined significantly in recent years. However, a few studies have implied that the prevalence is underestimated due to pregnancies with severe BDs often being terminated before 28 weeks of gestation. This study sought to contribute to this data conflict by determining the total prevalence of BDs throughout the entirety of pregnancies, depicting the epidemiological distribution of BDs in Shaanxi Province, and examining the impact of pregnancy termination before 28 weeks of gestation on overall BD prevalence. Methods: Based on data extracted from the provincial Birth Defects Surveillance Network in Shaanxi Province, from 2014 to 2020, the trends of 18 frequent, major BDs at any gestational age were analysed. Results: The total prevalence of BDs throughout pregnancy in Shaanxi Province increased significantly from 2014 to 2020, partly due to the inclusion of slight congenital heart diseases. It was also shown that the prevalence of all major types of BD had been previously underestimated, particularly severe external BDs, anywhere from 10% to 100% due to the previous sole measurement of terminations after 28 gestational weeks. Neural tube defects, however, remained one of the top five BDs with the highest total prevalence. Conclusions: The exclusion of pregnancy terminations <28 weeks of gestation resulted in a severe underestimation of the total birth prevalence of BDs, particularly severe external defects. To estimate the true population-level prevalence of BD better, the current BD surveillance system should include pregnancy terminations before 28 weeks of gestation.