Department of Obstetrics and Gynaecology, NIHR Cambridge Biomedical Research Centre, University of Cambridge, Cambridge, UK.
The Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
Health Technol Assess. 2021 Feb;25(15):1-190. doi: 10.3310/hta25150.
Currently, pregnant women are screened using ultrasound to perform gestational aging, typically at around 12 weeks' gestation, and around the middle of pregnancy. Ultrasound scans thereafter are performed for clinical indications only.
We sought to assess the case for offering universal late pregnancy ultrasound to all nulliparous women in the UK. The main questions addressed were the diagnostic effectiveness of universal late pregnancy ultrasound to predict adverse outcomes and the cost-effectiveness of either implementing universal ultrasound or conducting further research in this area.
We performed diagnostic test accuracy reviews of five ultrasonic measurements in late pregnancy. We conducted cost-effectiveness and value-of-information analyses of screening for fetal presentation, screening for small for gestational age fetuses and screening for large for gestational age fetuses. Finally, we conducted a survey and a focus group to determine the willingness of women to participate in a future randomised controlled trial.
We searched MEDLINE, EMBASE and the Cochrane Library from inception to June 2019.
The protocol for the review was designed a priori and registered. Eligible studies were identified using keywords, with no restrictions for language or location. The risk of bias in studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Health economic modelling employed a decision tree analysed via Monte Carlo simulation. Health outcomes were from the fetal perspective and presented as quality-adjusted life-years. Costs were from the perspective of the public sector, defined as NHS England, and the costs of special educational needs. All costs and quality-adjusted life-years were discounted by 3.5% per annum and the reference case time horizon was 20 years.
Umbilical artery Doppler flow velocimetry, cerebroplacental ratio, severe oligohydramnios and borderline oligohydramnios were all either non-predictive or weakly predictive of the risk of neonatal morbidity (summary positive likelihood ratios between 1 and 2) and were all weakly predictive of the risk of delivering a small for gestational age infant (summary positive likelihood ratios between 2 and 4). Suspicion of fetal macrosomia is strongly predictive of the risk of delivering a large infant, but it is only weakly, albeit statistically significantly, predictive of the risk of shoulder dystocia. Very few studies blinded the result of the ultrasound scan and most studies were rated as being at a high risk of bias as a result of treatment paradox, ascertainment bias or iatrogenic harm. Health economic analysis indicated that universal ultrasound for fetal presentation only may be both clinically and economically justified on the basis of existing evidence. Universal ultrasound including fetal biometry was of borderline cost-effectiveness and was sensitive to assumptions. Value-of-information analysis indicated that the parameter that had the largest impact on decision uncertainty was the net difference in cost between an induced delivery and expectant management.
The primary literature on the diagnostic effectiveness of ultrasound in late pregnancy is weak. Value-of-information analysis may have underestimated the uncertainty in the literature as it was focused on the internal validity of parameters, which is quantified, whereas the greatest uncertainty may be in the external validity to the research question, which is unquantified.
Universal screening for presentation at term may be justified on the basis of current knowledge. The current literature does not support universal ultrasonic screening for fetal growth disorders.
We describe proof-of-principle randomised controlled trials that could better inform the case for screening using ultrasound in late pregnancy.
This study is registered as PROSPERO CRD42017064093.
This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in ; Vol. 25, No. 15. See the NIHR Journals Library website for further project information.
目前，孕妇通过超声检查进行妊娠年龄检查，通常在妊娠 12 周左右，以及妊娠中期左右。此后，仅根据临床指征进行超声检查。
我们评估了向所有英国初产妇提供晚期妊娠超声检查的可能性。主要问题是晚期妊娠超声检查预测不良结局的诊断效果，以及实施普遍超声检查或在该领域进行进一步研究的成本效益。
我们对晚期妊娠的五项超声测量进行了诊断测试准确性评估。我们进行了成本效益和信息价值分析，用于筛查胎儿体位、筛查胎儿生长受限和筛查胎儿过大。最后，我们进行了一项调查和焦点小组，以确定妇女参与未来随机对照试验的意愿。
我们从建立到 2019 年 6 月在 MEDLINE、EMBASE 和 Cochrane 图书馆中进行了搜索。
该审查的方案是预先设计和注册的。使用关键词确定符合条件的研究，对语言或地点没有限制。使用 QUADAS-2 工具评估研究的偏倚风险。健康经济模型采用通过蒙特卡罗模拟进行分析的决策树。健康结果从胎儿的角度来看，并以质量调整生命年表示。成本从公共部门的角度来看，定义为英格兰国民保健服务（NHS England），以及特殊教育需求的成本。所有成本和质量调整生命年均按每年 3.5%贴现，参考案例时间范围为 20 年。
脐动脉血流多普勒流速、脑胎盘比、严重羊水过少和临界羊水过少均对新生儿发病率的风险无预测作用或仅有微弱预测作用（综合阳性似然比在 1 到 2 之间），对胎儿生长受限的风险均有微弱预测作用（综合阳性似然比在 2 到 4 之间）。怀疑胎儿巨大儿与分娩巨大儿的风险强烈相关，但与肩难产的风险仅呈弱相关，尽管具有统计学意义。很少有研究对超声检查结果进行盲法，并且由于治疗矛盾、确定偏倚或医源性伤害，大多数研究都被评为高偏倚风险。健康经济分析表明，根据现有证据，仅为胎儿体位进行普遍超声检查在临床和经济上都是合理的。包括胎儿生物测量的普遍超声检查具有边缘成本效益，并且对假设敏感。价值信息分析表明，对决策不确定性影响最大的参数是诱导分娩和期待管理之间的净成本差异。
关于晚期妊娠超声检查诊断效果的主要文献较弱。价值信息分析可能低估了文献中的不确定性，因为它侧重于参数的内部有效性，这是定量的，而最大的不确定性可能在于研究问题的外部有效性，这是未量化的。
基于目前的知识，普遍筛查足月时的体位可能是合理的。目前的文献不支持普遍使用超声筛查胎儿生长障碍。
我们描述了原理验证性随机对照试验，可以更好地为使用超声在晚期妊娠进行筛查提供信息。
本研究已在 PROSPERO CRD42017064093 注册。
本项目由英国国家卫生研究所（NIHR）健康技术评估计划资助，将在；第 25 卷，第 15 期。请访问 NIHR 期刊库网站以获取有关该项目的更多信息。
