ObjectiveTo investigate the incidence of severe postpartum haemorrhage among nulliparous women with a spontaneous onset of labour at term from 2000 to 2020.DesignPopulation‐based cohort study.SettingNational, using the Medical Birth Registry of Norway.PopulationWomen (n = 330 244) who gave birth to their first singleton child in a cephalic presentation after a spontaneous onset of labour at term.MethodsCross‐tabulations and regression analysis with generalised linear models were used to assess time trends and adjust for potential confounding factors. We also stratified the analyses by maternal age groups, obstetric interventions, mode of delivery and institution size. Time trends were analysed using periods of 5 or 6 years as a unit, and the period from 2000 to 2004 was used as the reference.Main outcome measuresSevere postpartum haemorrhage (PPH) was defined as blood loss of >1500 mL within 24 h and/or in combination with blood transfusion.ResultsSevere PPH occurred in 7601/330 244 (2.30%) women. The incidence increased from 1.24% in 2000–2004 to 3.83% in 2015–2020 (adjusted relative risk, aRR 2.90; 95% CI 2.70–3.12). Changes in maternal characteristics or obstetric interventions did not explain the increase, and we found similar increases across institutions of all sizes.ConclusionsThe incidence of severe PPH among nulliparous women increased almost threefold over 21 years. The current high incidence warrants urgent efforts to assess unknown risk factors, the health care provided and health system factors that may contribute to the increase, to inform improvements in care.

中文翻译：

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自然分娩的未产妇严重产后出血的趋势：一项基于人群的队列研究

目的调查 2000 年至 2020 年足月自然分娩的未产妇严重产后出血的发生率。设计基于人群的队列研究。SettingNational，使用挪威医学出生登记处。n= 330 244），他们在足月自发临产后以头位产下第一个单胎婴儿。方法使用广义线性模型的交叉表和回归分析来评估时间趋势并调整潜在的混杂因素。我们还按产妇年龄组、产科干预措施、分娩方式和机构规模对分析进行分层。以5年或6年为单位进行时间趋势分析，并以2000年至2004年为参考。 主要结局指标严重产后出血（PPH）定义为24小时内失血量>1500mL和/结果7601/330 244名(2.30%)女性发生严重PPH。发病率从2000-2004年的1.24%增加到2015-2020年的3.83%（调整后相对风险，aRR 2.90；95% CI 2.70-3.12）。产妇特征或产科干预措施的变化并不能解释这种增加，我们发现各种规模的机构都有类似的增加。 结论 21 年来，未生育妇女中严重 PPH 的发病率几乎增加了三倍。目前的高发病率需要紧急努力评估未知的风险因素、所提供的医疗保健以及可能导致发病率增加的卫生系统因素，以便为改善护理提供信息。