Birth defects, including congenital structural or functional abnormalities, remained a main cause of death among infants and represented a significant clinical and public health challenge (1). Periconceptional folic acid supplementation has been shown to effectively reduce the risk of pregnancies complicated with neural tube defects (NTDs) (2) and limb reduction (3). The prevalence of NTDs have decreased from 118.9/10,000 births to 31.5/10,000 in northern China from 2000 to 2014 and pre-perinatal (<28 gestational weeks) NTDs accounted for 60% of all NTDs (4).The trends of other birth defects among this population and the correlation with the folic-acid supplement program and population policy change had not been reported. This study aimed to examine the trends of selected structural birth defects (Supplementary Table S1) in 5 counties in Shanxi Province during 2000–2019 based on a population-based birth-defect surveillance system. The results showed that the prevalence of selected structural birth defects in the study area decreased significantly from 182.8/10,000 to 119.3/10,000 during the past two decades.
Data from a population-based birth-defect surveillance system that covered 5 counties (Pingding, Xiyang, Taigu, Zezhou, and Shouyang) in Shanxi Province from 2000 to 2019 were analyzed in this study (Supplemental Figure S1). Details of the birth defects surveillance system were described in our previous publication (4). Briefly, the system was established in the early 2000s, and more than 20,000 births were covered each year. All pregnant women residing in the study area for more than 1 year were monitored. All livebirths or stillbirths of 28 or more complete gestational weeks and pregnancy terminations at any gestational age following the prenatal diagnosis of birth defects were included. The surveillance data covered more than 95% of live births and data quality was ensured. Information on the diagnostic criteria of birth defects (coded according to International Statistical Classification of Diseases and Related Health Problems, 10th revision), sex, gestational weeks, birth outcome and maternal residence was collected. The study protocol was reviewed and approved by the Institutional Review Board of Peking University.
The prevalence at birth of birth defects by year/period, by type, and by gestational week’s group was compared using chi-squared tests. Perinatal prevalence (cases of 28 or more gestational weeks) and pre-perinatal prevalence (cases before 28 gestational weeks) were calculated, and 5 periods of time were demarcated according to population policy and public strategy. Two-tailed p≤0.05 was considered statistically significant. All statistical analyses were performed using the SPSS package (version 18.0, SPSS Inc., Chicago, IL, USA).
From 2000 to 2019, a total of 293,573 births were covered and 4,748 infants with 5,845 cases of structural birth defects (an infant may have multiple birth defects) were recorded in the system.
Perinatal structural birth defects decreased from 83.9% of all birth defects in 2000 to 59.9% in 2019 (Figure 1A) (Pearson chi-squared tests: 62.958, p<0.05) and the perinatal prevalence decreased dramatically from a peak of 139.6/10,000 births in 2003 to 74.7/10,000 in 2019 (Figure 1B).
Figure 1. Selected structural birth defects by gestational weeks and year in 5 counties, Shanxi Province, China, 2000–2019. (A) Proportion of birth defects; (B) Prevalence of birth defects.
Prevalence of nervous system defects was the highest and decreased from 169/10,000 births to 35/10,000 in the past two decades. Musculoskeletal system defects remained the second most common birth defect and fluctuated between 29/10,000 to 39/10,000. Cleft lip with or without cleft palate ranked third and decreased from 27/10,000 to 17/10,000 during 2000–2019 (Table 1, Figure 2A).
ICD-10 code Classification Gestational weeks <28 weeks ≥28 weeks Total 1. Q00–Q07 The nervous system 1,987 (67.68) 1,206 ( 41.08) 3,193 (108.76) 2. Q10–Q18 Eye, ear, face and neck 1 ( 0.03) 139 ( 4.73) 140 ( 4.77) 3. Q20–Q28 The circulatory system 33 ( 1.12) 51 ( 1.74) 84 ( 2.86) 4. Q35–Q37 Cleft lip and cleft palate 81 ( 2.76) 614 ( 20.91) 695 ( 23.67) 5. Q38–Q45 The digestive system 4 ( 0.14) 119 ( 4.05) 123 ( 4.19) 6. Q50–Q56 Genital organs 0 79 ( 2.69) 79 ( 2.69) 7. Q60–Q64 The urinary system 3 ( 0.10) 7 ( 0.24) 10 ( 0.34) 8. Q65–Q79 The musculoskeletal system 122 ( 4.16) 816 ( 27.80) 938 ( 31.95) 9. Q80–Q89 Other congenital malformations 181 ( 6.17) 381 ( 12.98) 562 ( 19.14) 10. Q90–Q99 Chromosomal abnormalities 16 ( 0.55) 5 ( 0.17) 21 ( 0.72) Total* 2,428 (82.71) 3,417 (116.39) 5,845 (199.10) *The number of cases in this table was based on birth defect phenotypes, not the person. One person may have one more birth defects, so the total number of birth defects was greater than the cases.
Table 1. Total number and prevalence (1/10,000) of birth defects by gestational weeks and system in 5 counties, Shanxi Province, China, 2000−2019.
Figure 2. Prevalence of congenital abnormality by period in 5 counties, Shanxi Province, China, 2000–2019. (A) Pooled birth defects by system; (B) The nervous system defects by subtype; (C) The nervous system defects by gestational weeks. The 5 periods were divided according to population policy and public strategy, i.e., 2000–2003 (Period of mandatory pre-marital physical check-ups), 2004–2008 (Period of voluntary pre-marital physical check-ups and before folic acid supplementation), 2009–2011 (Period of after folic acid supplementation), 2012–2015 (Period of population policy transition) and 2016–2019 (Period of universal two-child policy). Abbreviations: CNS=central nervous system, CL/P=cleft lip and cleft palate.
Among the selected birth defects, NTDs including anencephaly, spina bifida, and encephalocele and congenital hydrocephalus decreased significantly (Figure 2B). Anencephaly decreased from 62/10,000 live births in 2000–2003 to 9/10,000 in 2016–2019, and congenital hydrocephalus decreased from 29/10,000 to 8/10,000 during this period. The prevalence of spina bifida and encephalocele was estimated to decrease 75% during 2000–2019.
For congenital abnormalities of the nervous system, the prevalence decreased during 2000–2019, especially for perinatal prevalence, while the pre-perinatal prevalence increased from 73/10,000 births in 2000–2003 to 91/10,000 in 2004–2008, and then decreased to 75/10,000 in 2009–2011 to 30/10,000 in 2016–2019 (Figure 2C).