Table_1_Ethnic differences in preterm birth in Southwest China, 2014-2018: A population-based observational study.pdf

ObjectivePreterm birth is a major healthcare problem and has been rising gradually in the past three decades in China. Yet the ethnic differences in the rates and distributions of preterm birth remain largely unknown in China. This study used data from Yunnan, a multiethnic province, to explore the differences in preterm birth across ethnicities.
MethodsA population-based observational study was conducted based on data from the National Free Preconception Health Examination Project in rural Yunnan from Jan 1, 2014 to Dec 31, 2018. Pregnancies with at least one livebirth were included in this study. We estimated the rates and 95% confidence intervals (CIs) of overall preterm birth (born < 37 weeks’ gestation), moderate to late preterm birth (born between 32 and <37 weeks’ gestation), very preterm birth (born between 28 and 31 weeks’ gestation), and extremely preterm birth (born < 28 weeks’ gestation) across maternal ethnicity and compared them using log-binomial regressions. Multivariable log-binomial regressions were used to assess the association between maternal ethnicity and preterm birth with adjustment for potential confounders, including year of delivery, maternal age at delivery, education, occupation, pre-pregnancy body mass index, history of chronic disease, history of preterm birth, smoking and drinking alcohol during early pregnancy, and parity and multiple pregnancy of current pregnancy.
ResultsAmong 195,325 women who delivered at least one live baby, 7.90% (95% CI, 7.78–8.02%) were born preterm. The rates of moderate to late preterm birth, very preterm birth, and extremely preterm birth were 6.20% (95% CI, 6.09–6.30%), 1.18% (95% CI, 1.13–1.23%), and 0.52% (95% CI, 0.49–0.56%), respectively. The rates of overall preterm birth, moderate to late preterm birth, very preterm birth, and extremely preterm birth differed across maternal ethnicity. The preterm birth rates in Dai (10.73%), Miao (13.23%), Lisu (12.64%), Zhuang (11.77%), Wa (10.52%), and Lagu (12.34%) women were significantly higher than that in Han women, and the adjusted relative risks were 1.45 [95% CI, 1.36, 1.54], 1.74 (95% CI, 1.62, 1.86), 1.60 (95% CI, 1.47, 1.75), 1.60 (95% CI, 1.46, 1.75), 1.40 (95% CI, 1.22, 1.60), and 1.67 (95% CI, 1.50, 1.87) respectively. There was no difference in preterm birth rate between Han women and Hani, Bai, or Hui women.
ConclusionThis study found notable differences in the rates of preterm birth and its sub-categories across maternal ethnicities, which were especially higher in ethnic minority women. The findings suggest that greater efforts to reduce ethnic inequalities in preterm birth. Future studies are warranted to understand the drivers of ethnic inequalities in preterm birth in China.

研究背景与目的：早产是重大公共卫生问题，近三十年来中国的早产发生率呈逐步上升趋势。然而，目前中国早产发生率及分布的民族差异仍不明确。本研究依托多民族省份云南的相关数据，探讨不同民族间早产发生情况的差异。

研究方法：本研究基于2014年1月1日至2018年12月31日云南省农村地区国家免费孕前健康检查项目的数据，开展了一项以人群为基础的观察性研究。本研究纳入所有至少存在1次活产的妊娠案例。研究人员估算了不同民族孕产妇的总体早产（妊娠<37周分娩）、中晚期早产（妊娠32~<37周分娩）、极早产（妊娠28~31周分娩）和极早早产（妊娠<28周分娩）的发生率及95%置信区间（confidence intervals, CIs），并采用对数二项回归进行组间比较。此外，采用多变量对数二项回归分析孕产妇民族与早产的关联，并对潜在混杂因素进行校正，包括分娩年份、孕产妇分娩年龄、受教育程度、职业、孕前体重指数、慢性病史、早产史、孕早期吸烟饮酒史，以及当前妊娠的产次与多胎妊娠情况。

研究结果：在195325名至少生育1名活婴的女性中，7.90%（95%CI：7.78%~8.02%）发生了早产。其中，中晚期早产、极早产和极早早产的发生率分别为6.20%（95%CI：6.09%~6.30%）、1.18%（95%CI：1.13%~1.23%）和0.52%（95%CI：0.49%~0.56%）。不同民族孕产妇的总体早产、中晚期早产、极早产及极早早产发生率均存在显著差异。傣族（10.73%）、苗族（13.23%）、傈僳族（12.64%）、壮族（11.77%）、佤族（10.52%）和拉祜族（12.34%）孕产妇的早产率均显著高于汉族孕产妇，校正后的相对风险分别为1.45[95%CI：1.36, 1.54]、1.74（95%CI：1.62, 1.86）、1.60（95%CI：1.47, 1.75）、1.60（95%CI：1.46, 1.75）、1.40（95%CI：1.22, 1.60）和1.67（95%CI：1.50, 1.87）。汉族孕产妇与哈尼族、白族或回族孕产妇的早产率无显著差异。

结论：本研究发现，不同民族孕产妇的早产总体发生率及其亚类发生率存在显著差异，少数民族孕产妇的早产风险尤为偏高。研究结果提示，应加大力度缩小早产发生的民族间不平等性。未来仍需开展进一步研究，以阐明中国早产发生民族差异的潜在驱动因素。