Authors' objectives: Smallness for gestational age has been associated with an increased risk of neonatal/fetal adverse outcomes. The Healthcare Safety Investigation Branch has issued a safety recommendation aimed at improving fetal growth monitoring strategies and reducing risk for babies. The objective was to summarise available evidence to inform the Healthcare Safety Investigation Branch recommendation. The review comprised four research questions on: effects of fetal growth monitoring on neonatal/parental outcomes; effects of implementing fetal growth monitoring guidelines on neonatal/parental outcomes; accuracy of fetal growth monitoring strategies for predicting smallness for gestational age neonates/fetal growth restriction and factors affecting the accuracy of fetal growth monitoring strategies. Smallness for gestational age has been found to be associated with a higher risk of stillbirth. According to the latest report by the Office for National Statistics, low birthweight (BW) is one of the key risk factors for neonatal and infant mortality in England and Wales. In the UK, pregnant people are typically screened using ultrasound (US) at around 12 weeks of gestation and approximately at the middle of pregnancy for gestational aging. After mid-pregnancy, they are offered further US monitoring, to assess fetal growth, only where clinically indicated. The Healthcare Safety Investigation Branch (HSIB) 2021 National Learning Report, ‘Intrapartum stillbirth: learning from maternity safety investigations that occurred during the COVID-19 pandemic, 1 April to 30 June 2020’, identified 11 cases of stillborn small for gestational age (SGA) infants, of whom 8 were not detected until birth, a finding which could be viewed as a further indication of the poor sensitivity of the methods currently used to detect SGA. The HSIB Report made eight safety recommendations, including Safety recommendation R/2021/148: HSIB recommends that the Department of Health and Social Care commission a review to improve the reliability of existing assessment tools for fetal growth and fetal heart rate to minimise the risk for babies. This systematic review has been commissioned and undertaken to summarise the available evidence to inform the fetal growth monitoring component of this recommendation. The overall objective of this project was to summarise the available evidence to inform the fetal growth monitoring component of the HSIB safety recommendation to ‘commission a review to improve the reliability of existing assessment tools for fetal growth and fetal heart rate to minimise the risk for babies’. The following research questions were defined to address the project objectives: What are the effects, on clinical outcomes [e.g. neonatal morbidity, rates of brain injury, unplanned neonatal intensive care unit (NICU) admissions and parental morbidity] and rates of stillbirth and neonatal death, of interventions (e.g. iatrogenic delivery) which are made based on the findings of fetal growth monitoring to detect SGA/fetal growth restriction (FGR)? What are the effects of fetal growth monitoring to detect SGA/FGR on rates of pre-term iatrogenic delivery and gestational age at iatrogenic delivery? What are the effects, on neonatal and parental outcomes, of implementing published guidelines for fetal growth monitoring? What is the accuracy of different methods of monitoring fetal growth, for example, symphysis fundal height, US measurement of fetal size [fetal abdominal circumference (AC) or estimated fetal weight (EFW)], for predicting SGA/FGR at delivery? What are the effects, on the performance (accuracy) of different methods of monitoring fetal growth, of key operational variables [e.g. timing of monitoring, type of growth reference chart used (customised or population-based), experience and training of clinical practitioner performing monitoring] and parental characteristics [e.g. body mass index (BMI)/obesity and ethnicity]? What factors affect the failure to obtain a satisfactory measurement or lack of clinical confidence in the reported result?

Authors' results and conclusions: Fifty-eight studies (78 publications) were included in the review. Q1 – Antenatal identification of smallness for gestational age pregnancies was associated with increased rates of intervention (two retrospective cohort studies, n = 100, 198 and 2928), but the available evidence did not support an effect on stillbirths or neonatal outcomes. Q2 – Meta-analysis (three observational studies and one randomised controlled trial, n = 318,523) indicated that implementation of the Growth Assessment Protocol was associated with a reduction in the risk of stillbirth and risk ratio of 0.79 (95% confidence interval 0.74 to 0.84). Meta-analyses (one observational study and one randomised controlled trial, n = 11,978) indicated that Growth Assessment Protocol implementation was associated with a reduction in the risk of 5-minute Apgar score

Authors' methods: Nineteen databases were searched from 2000 to March 2023 and were updated September 2023. Pregnant people with and without risk factors were included. Each review question had further eligibility criteria. For accuracy results, summary estimates of the sensitivity and specificity with 95% confidence intervals for the prediction of smallness for gestational age at delivery were calculated. Random-effects models were used for the meta-analysis of clinical outcomes. Further outcomes, including the results of risk of bias assessments, were summarised narratively. There is limited evidence linking fetal growth monitoring tests results to the changes in fetal/neonatal outcomes. There is some evidence supporting the reduction of adverse outcomes by Growth Assessment Protocol implementation. Testing during the third trimester is likely to result in more accurate prediction of smallness for gestational age at birth than earlier testing. Use of a locally derived reference chart for estimated fetal weight may result in optimised sensitivity for a given birthweight reference chart (definition of smallness for gestational age). Assessment of clinical effectiveness Nineteen databases, including MEDLINE and EMBASE, research registers, a conference proceedings resource and a pre-print resource were searched for relevant studies from 2000 to March 2023. The main EMBASE and MEDLINE searches were rerun in their entirety in September 2023. Search results were screened for relevance independently by two reviewers. Full-text inclusion assessment, data extraction and quality assessment were conducted by one reviewer and were checked by a second. The methodological quality of included diagnostic test accuracy (DTA) studies was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). The methodological quality of included randomised controlled trials (RCTs) was assessed using the revised Cochrane Risk of Bias Tool for Randomised Trials (RoB 2). The methodological quality of observational ‘before-and-after’ studies was assessed using a checklist, devised by the authors, for this review. Where multiple accuracy studies assessed the same growth monitoring strategy, summary estimates of the sensitivity and specificity together with 95% confidence intervals (CIs) and prediction regions for the prediction of SGA at delivery were calculated. All meta-analyses involved fewer than four studies and estimated separate pooled estimates of sensitivity and specificity, using random-effects logistic regression. For comparative studies that evaluated the same clinical outcome(s), intervention/monitoring method and comparator, summary effect estimates with 95% CIs were calculated via random-effects models using the Mantel–Haenszel method with a Paule-Mandel estimator. Where between-study heterogeneity limited the applicability of meta-analysis, a narrative summary utilising text, tables and figures has been provided. The Results of the assessment of clinical effectiveness section of this report is structured by research question.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hta/NIHR135862

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hta/AJLK7403

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/AJLK7403

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk