Supplementary Material for: The incidence of necrotizing enterocolitis and late-onset sepsis during the COVID-19 pandemic in Sweden: A population-based cohort study

Introduction: The effect of the pandemic restrictions in the NICUs is not well studied. Necrotizing enterocolitis (NEC) is characterized by intestinal inflammation and bacterial invasion. This study aimed to investigate whether the incidence of NEC has changed during the COVID-19 pandemic in Sweden and whether it was associated with a change in the frequency of extremely preterm births.
Methods: Data were retrieved from the Swedish Neonatal Quality Register (SNQ) for infants registered between January 2017 and December 2021 born below a gestational age of 35 weeks. The registry completeness is 98-99%. The diagnosis of NEC was the primary outcome. Generalized linear model analysis was used to calculate the risk ratio for NEC.
Results: Totally 13239 infants were included. 235 (1.8%) infants developed NEC, out of which 91 required surgical treatment. 8967 infants were born before COVID-19 pandemic and 4272 during. Median gestational age at birth was 32.8 weeks in both periods. The incidence of NEC was significantly lower during COVID-19 pandemic compared to the prior period (1.43% vs 1.94% p 0.037), but not the incidence of surgical NEC. The crude Risk ratio of developing NEC during COVID-19 pandemic was 0.74 (95% CI(0.55-0.98)). The incidence of Late onset sepsis with positive culture was also declined during COVID-19 (3.21% vs 4.15%, p value 0.008).
Conclusion: While we found significant reduction in the incidence of NEC and culture-positive late-onset sepsis during the COVID-19 pandemic, the number of extremely preterm births was unchanged.

引言：目前针对新生儿重症监护病房（Neonatal Intensive Care Unit, NICU）的疫情防控措施所产生的影响尚未得到充分研究。坏死性小肠结肠炎（Necrotizing enterocolitis, NEC）以肠道炎症及细菌侵袭为特征。本研究旨在探讨瑞典新冠疫情期间坏死性小肠结肠炎的发病率是否发生变化，以及其是否与极早早产儿出生率的变化相关。
研究方法：本研究数据来源于瑞典新生儿质量登记系统（Swedish Neonatal Quality Register, SNQ），纳入2017年1月至2021年12月期间登记的胎龄小于35周的新生儿。该登记系统的信息完整度为98%~99%。本研究的主要结局指标为坏死性小肠结肠炎的确诊情况，采用广义线性模型分析计算坏死性小肠结肠炎的风险比。
研究结果：本研究共纳入13239名新生儿，其中235名（1.8%）发生坏死性小肠结肠炎，91名需接受外科手术治疗。新冠疫情前纳入新生儿8967名，疫情期间纳入4272名。两个时期新生儿的出生胎龄中位数均为32.8周。相较于疫情前期，新冠疫情期间坏死性小肠结肠炎的发病率显著降低（1.43% vs 1.94%，p=0.037），但外科手术治疗型坏死性小肠结肠炎的发病率无显著差异。新冠疫情期间发生坏死性小肠结肠炎的粗风险比为0.74（95%置信区间：0.55~0.98）。新冠疫情期间，培养阳性晚发性脓毒症的发病率亦有所下降（3.21% vs 4.15%，p=0.008）。
研究结论：本研究发现，新冠疫情期间坏死性小肠结肠炎与培养阳性晚发性脓毒症的发病率均显著降低，但极早早产儿的出生率未发生明显改变。