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      Customised and Noncustomised Birth Weight Centiles and Prediction of Stillbirth and Infant Mortality and Morbidity: A Cohort Study of 979,912 Term Singleton Pregnancies in Scotland

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          Abstract

          Background

          There is limited evidence to support the use of customised centile charts to identify those at risk of stillbirth and infant death at term. We sought to determine birth weight thresholds at which mortality and morbidity increased and the predictive ability of noncustomised (accounting for gestational age and sex) and partially customised centiles (additionally accounting for maternal height and parity) to identify fetuses at risk.

          Methods

          This is a population-based linkage study of 979,912 term singleton pregnancies in Scotland, United Kingdom, between 1992 and 2010. The main exposures were noncustomised and partially customised birth weight centiles. The primary outcomes were infant death, stillbirth, overall mortality (infant and stillbirth), Apgar score <7 at 5 min, and admission to the neonatal unit. Optimal thresholds that predicted outcomes for both non- and partially customised birth weight centiles were calculated. Prediction of mortality between non- and partially customised birth weight centiles was compared using area under the receiver operator characteristic curve (AUROC) and net reclassification index (NRI).

          Findings

          Birth weight ≤25th centile was associated with higher risk for all mortality and morbidity outcomes. For stillbirth, low Apgar score, and neonatal unit admission, risk also increased from the 85th centile. Similar patterns and magnitude of associations were observed for both non- and partially customised birth weight centiles. Partially customised birth weight centiles did not improve the discrimination of mortality (AUROC 0.61 [95%CI 0.60, 0.62]) compared with noncustomised birth weight centiles (AUROC 0.62 [95%CI 0.60, 0.63]) and slightly underperformed in reclassifying pregnancies to different risk categories for both fatal and non-fatal adverse outcomes (NRI -0.027 [95% CI -0.039, -0.016], p < 0.001). We were unable to fully customise centile charts because we lacked data on maternal weight and ethnicity. Additional analyses in an independent UK cohort ( n = 10,515) suggested that lack of data on ethnicity in this population (in which national statistics show 98% are white British) and maternal weight would have misclassified ~15% of the large-for-gestation fetuses.

          Conclusions

          At term, birth weight remains strongly associated with the risk of stillbirth and infant death and neonatal morbidity. Partial customisation does not improve prediction performance. Consideration of early term delivery or closer surveillance for those with a predicted birth weight ≤25th or ≥85th centile may reduce adverse outcomes. Replication of the analysis with fully customised centiles accounting for ethnicity is warranted.

          Abstract

          In an analysis of 979,912 term singleton pregnancies, Stamatina Iliodromiti and colleagues compare using customised and noncustomised birth weight centiles for prediction of stillbirth and infant mortality and morbidity.

          Author Summary

          Why Was This Study Done?
          • In developed countries, one-third of stillbirths and infant deaths occur at term.

          • There are multiple clinical definitions at term of what constitutes a small- or large-for-gestation fetus, with <10th centile and >90th centile commonly used. Whether these statistical thresholds can accurately identify fetuses at risk of mortality or morbidity is unknown.

          • Customised birth weight centiles (accounting for sex, gestation, and maternal characteristics) are increasingly being adopted by many maternity units. However, whether they can identify term fetuses at risk of death more accurately than noncustomised centiles is unknown.

          What Did The Researchers Do And Find?
          • We examined data on 979,912 term singleton pregnancies over a 19-y period in Scotland. With external validation of our findings on an independent UK cohort ( n = 10,515).

          • We studied the associations of birth weight centiles (noncustomised and partially customised) with stillbirth, infant mortality, admission to the neonatal unit and Apgar score <7 at 5 min. In addition, we assessed whether partially customised centiles perform better in predicting adverse outcomes compared with noncustomised centiles. We were unable to assess fully customised centiles as we did not have data on maternal ethnicity and weight.

          • We found that birth weight ≤25th or ≥85th centile (both partially and noncustomised) are associated with greater risk of adverse outcomes. Partially customised centiles did not identify more fetuses at risk of death compared with noncustomised centiles.

          What Do These Findings Mean?
          • Adverse outcomes frequently occur in term fetuses. Closer surveillance or earlier delivery of those fetuses with a predicted birth weight ≤25th or ≥85th centile may reduce adverse outcomes.

          • Replication of the analysis with fully customised birth weight centiles is required.

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          Most cited references21

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          • Abstract: found
          • Article: not found

          Racial/ethnic standards for fetal growth: the NICHD Fetal Growth Studies.

          Fetal growth is associated with long-term health yet no appropriate standards exist for the early identification of undergrown or overgrown fetuses. We sought to develop contemporary fetal growth standards for 4 self-identified US racial/ethnic groups.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            A systematic review of the ultrasound estimation of fetal weight.

            The range and use of ultrasound fetal measurements have gradually been extended. Measurements have been combined to estimate fetal weight by mathematically based non-linear regression analysis or physically based volumetric methods. Fetal weight estimation is inaccurate, with poor sensitivity for prediction of fetal compromise. Several authors have shown the unacceptable level of intra- and interobserver variability in fetal measurement and the impact of errors on growth assessment. The aims of this study were to review the available methods and possible sources of inaccuracy. Four databases were searched for studies comparing ultrasound estimated fetal weight (EFW) with birth weight. Studies meeting the inclusion criteria evaluated 11 different methods. Errors were graphically summarized. No consistently superior method has emerged. Volumetric methods provide some theoretical advantages. Random errors are large and must be reduced if clinical errors are to be avoided. The accuracy of EFW is compromised by large intra- and interobserver variability. Efforts must be made to minimize this variability if EFW is to be clinically useful. This may be achieved through averaging of multiple measurements, improvements in image quality, uniform calibration of equipment, careful design and refinement of measurement methods, acknowledgment that there is a long learning curve, and regular audit of measurement quality. Further work to improve the universal validity and accuracy of fetal weight estimation formulae is also required. Copyright (c) 2004 ISUOG.
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              • Record: found
              • Abstract: found
              • Article: not found

              Neonatal respiratory morbidity and mode of delivery at term: influence of timing of elective caesarean section.

              To establish whether the timing of delivery between 37 and 42 weeks gestation influences neonatal respiratory outcome and thus provide information which can be used to aid planning of elective delivery at term. All cases of respiratory distress syndrome or transient tachypnoea at term requiring admission to the neonatal intensive care unit were recorded prospectively for nine years. Rosie Maternity Hospital, Cambridge. During this time 33,289 deliveries occurred at or after 37 weeks of gestation. This information enabled calculation of the relative risk of respiratory morbidity for respiratory distress syndrome or transient tachypnoea in relation to mode of delivery and onset of parturition for each week of gestation at term. The incidence of respiratory distress syndrome at term was 2.2/1000 deliveries (95% CI; 1.7-2.7). The incidence of transient tachypnoea was 5.7/1000 deliveries (95% CI; 4.9-6.5). The incidence of respiratory morbidity was significantly higher for the group delivered by caesarean section before the onset of labour (35.5/1000) compared with caesarean section during labour (12.2/1000) (odds ratio, 2.9; 95% CI 1.9-4.4; P < 0.001), and compared with vaginal delivery (5.3/1000) (odds ratio, 6.8; 95% CI 5.2-8.9; P < 0.001). The relative risk of neonatal respiratory morbidity for delivery by caesarean section before the onset of labour during the week 37+0 to 37+6 compared with the week 38+0 to 38+6 was 1.74 (95% CI 1.1-2.8; P < 0.02) and during the week 38+0 to 38+6 compared with the week 39+0 to 39+6 was 2.4 (95% CI 1.2-4.8; P < 0.02). A significant reduction in neonatal respiratory morbidity would be obtained if elective caesarean section was performed in the week 39+0 to 39+6 of pregnancy.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                PLoS Med
                PLoS Med
                plos
                plosmed
                PLoS Medicine
                Public Library of Science (San Francisco, CA USA )
                1549-1277
                1549-1676
                31 January 2017
                January 2017
                : 14
                : 1
                : e1002228
                Affiliations
                [1 ]School of Medicine, University of Glasgow, Glasgow Royal Infirmary, Glasgow, United Kingdom
                [2 ]Institute of Health and Wellbeing, University of Glasgow, Glasgow, United Kingdom
                [3 ]Department of Obstetrics and Gynaecology, University of Cambridge, Rosie Hospital, Cambridge, United Kingdom
                [4 ]NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom
                [5 ]Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
                [6 ]MRC Integrative Epidemiology Unit at the University of Bristol, Bristol, United Kingdom
                University of Manchester, UNITED KINGDOM
                Author notes

                I have read the journal's policy and the authors of this manuscript have the following competing interests: GCSS receives/has received research support from GE, Roche and GSK. GCSS has been paid to attend advisory boards by GSK and Roche. GCSS has acted as a paid consultant to GSK. GCSS has received support to attend a scientific meeting from Chiesi. GCSS is named inventor in a patent submitted by GSK (UK) for novel application of an existing GSK compound for the prevention of preterm birth (PCT/EP2014/062602). GCSS has acted as an expert witness. GCSS is a member of a Data Safety Monitoring Committee for a trial of an RSV vaccine in pregnancy, being run by GSK. Please note: none of these directly relate to the paper, but GCSS states them for full disclosure. GCSS is a member of the Editorial Board of PLOS Medicine. In addition to grant funding that is acknowledged in the paper and that was relevant to the conduct of the study reported in the paper, DAL's institution has received funds from public, charity, and industry funders from grants on which DAL is the Principal application (UK Medical Research Council, UK Economic and Social Research Council, UK National Institute of Health Research, Wellcome Trust, British Heart Foundation, Roche Diagnostics, Ferring Pharmaceuticals, and Medtronic PLC). These funders had no impact on any aspect of the work presented in this paper.

                • Conceptualization: SI JPP DAL GCSS NS SMN.

                • Formal analysis: SI DFM DAL.

                • Methodology: JPP DFM.

                • Validation: SI SMN.

                • Writing – original draft: SI SMN.

                • Writing – review & editing: SI DFM JPP DAL GCSS NS SMN.

                Author information
                http://orcid.org/0000-0003-2124-0997
                http://orcid.org/0000-0002-6793-2262
                Article
                PMEDICINE-D-16-02659
                10.1371/journal.pmed.1002228
                5283655
                28141865
                8e398369-b5c0-4887-bc21-9b6dd0d56e61
                © 2017 Iliodromiti et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 17 August 2016
                : 20 December 2016
                Page count
                Figures: 2, Tables: 3, Pages: 16
                Funding
                Funded by: funder-id http://dx.doi.org/10.13039/501100000265, Medical Research Council;
                Award ID: MR/N015177/1
                Award Recipient :
                SI is funded by a UK Medical Research Council skills development fellowship (MR/N015177/1). DAL works in a Unit that receives funding from the University of Bristol and the UK Medical Research Council (MC_UU_12013/5); she is a National Institute of Health Research (NIHR) Senior Investigator (NF-SI-0611-10196). This work is also supported by the NIHR through the University of Bristol NIHR Biomedical Research Centre (BRC) and the University of Cambridge BRC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Biology and Life Sciences
                Physiology
                Physiological Parameters
                Body Weight
                Birth Weight
                Medicine and Health Sciences
                Physiology
                Physiological Parameters
                Body Weight
                Birth Weight
                Medicine and Health Sciences
                Women's Health
                Obstetrics and Gynecology
                Stillbirths
                Medicine and Health Sciences
                Women's Health
                Maternal Health
                Birth
                Labor and Delivery
                Medicine and Health Sciences
                Women's Health
                Obstetrics and Gynecology
                Birth
                Labor and Delivery
                Medicine and Health Sciences
                Health Care
                Health Statistics
                Morbidity
                Biology and Life Sciences
                Developmental Biology
                Neonates
                Medicine and Health Sciences
                Women's Health
                Maternal Health
                Pregnancy
                Medicine and Health Sciences
                Women's Health
                Obstetrics and Gynecology
                Pregnancy
                Medicine and Health Sciences
                Epidemiology
                Ethnic Epidemiology
                People and Places
                Population Groupings
                Age Groups
                Children
                Infants
                People and Places
                Population Groupings
                Families
                Children
                Infants
                Custom metadata
                Data used in this study are available from Services Division (ISD) ( www.isdscotland.org) of the National Services Scotland subject to approval by The Privacy Advisory Committee.

                Medicine
                Medicine

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