Supplementary Material for: Optimal strategies for screening common birth defects in children of lower- and middle-income countries: a systematic review

Introduction
Congenital anomalies are one of the major causes of the global burden of diseases, and low- and middle-income countries (LMIC) are disproportionately affected. This review assesses the prenatal and postnatal screening methods and compares the prevalence of major congenital anomalies in LMICs.
Methodology
We conducted a systematic search in MEDLINE/PubMed, CINAHL, Cochrane databases of systematic reviews, clinical trials.gov for relevant studies using Medical Subject Headings (MESH) and keywords. We categorized the studies into different systems and screening methods depending on the time the tests were conducted (prenatal or post-natal). The studies were then subjected to detailed descriptive analysis.
Results
A total of 59 studies were selected for analysis; these focused on screening methods for congenital anomalies and compared their prevalence with regards to different systems. The most common screening techniques both prenatal and post-natal included antenatal ultrasound, fetal echocardiography, pulse oximetry and clinical examination. The most common congenital abnormalities involved the central nervous system (neural tube defects) and musculoskeletal (clubfoot), followed by gastrointestinal (omphalocele and gastroschisis) and cardiovascular (structural heart defect) . Overall, different systems had varying prevalences of different birth defects, ranging from 0.28 to 8.5%. In contrast, the prevalence of musculoskeletal system disorders varied from 1.01% to 3.96%, in the cardiovascular system from 0.57% to 10.4%, and in the urogenital group from 0.83% to 5.9%.
Conclusion:
The review highlights the lack of screening programs and studies especially in the primary and secondary care settings in LMICs, and limited studies do indicate a high burden of various congenital anomalies. There is a need for guidelines and programs in global maternal and child health programs to include timely screening and management of common birth defects in LMICs.

引言
先天性异常（Congenital anomalies）是全球疾病负担的主要诱因之一，而低收入和中等收入国家（LMIC）受其影响尤为严重。本综述旨在评估产前与产后筛查手段，并对比低收入和中等收入国家中各类主要先天性异常的患病率。

研究方法
本研究通过医学主题词表（MESH）与关键词，在MEDLINE/PubMed、CINAHL、Cochrane系统综述数据库以及ClinicalTrials.gov中开展系统性检索，以获取相关研究文献。依据检测实施时机（产前或产后），将纳入的研究按不同系统与筛查手段进行分类，随后对其展开详细描述性分析。

研究结果
本研究共纳入59项针对先天性异常筛查手段的分析研究，并对比了不同系统类别的出生缺陷患病率。产前与产后最常用的筛查技术包括产前超声检查、胎儿超声心动图、脉搏血氧仪检测以及临床体格检查。最常见的先天性异常涉及中枢神经系统（神经管缺陷）与肌肉骨骼系统（马蹄内翻足），其次为消化系统（脐膨出与腹裂）与心血管系统（结构性心脏缺陷）。总体而言，不同系统类别的出生缺陷患病率存在差异，区间为0.28%至8.5%。其中，肌肉骨骼系统疾病的患病率区间为1.01%至3.96%，心血管系统为0.57%至10.4%，泌尿生殖系统为0.83%至5.9%。

结论
本综述指出，低收入和中等收入国家普遍缺乏针对先天性异常的筛查方案与相关研究，尤其是在基层与二级医疗保健机构中；现有有限的研究亦表明，当地各类先天性异常负担沉重。全球母婴健康项目亟需制定相关指南与方案，将低收入和中等收入国家常见出生缺陷的及时筛查与管理纳入其中。