Australian and New Zealand Journal of Obstetrics and Gynaecology 2015; 55: 1–2
DOI: 10.1111/ajo.12320
Editorial
Fetal growth: too big, too little, just right In recognition of the increased short- and long-term complication rates for the extremes of fetal weight, an assessment of fetal size (either clinical and/or sonographic) is routinely performed as a core component of prenatal care. It therefore is disappointing that (a) there is inconsistency in the definitions of fetal growth anomalies, (b) there is currently no internationally accepted standard for assessing fetal growth, (c) available techniques to identify both the macrosomic and the growth-restricted fetus are hounded by poor sensitivity and specificity, and (d) there are few interventions, particularly for the growth-restricted fetus, that modify the intrauterine growth trajectory. Why is the prenatal determination of fetal growth abnormalities so problematic? Firstly, the definition of abnormal fetal growth is imprecise with variation between publications and no currently accepted single international standard for assessing fetal growth. The definition of fetal growth restriction fundamentally represents the failure of a fetus to reach its growth potential; however, definitions range from the third, the fifth to the tenth percentile for any given gestation1 and a broad range of ultrasound fetal growth reference charts is used, both in publications and clinical practice.1,2 Similarly, for fetal macrosomia, the definition varies from an estimated fetal weight >90th percentile for a given gestation or a birthweight >4000– 4500 g independent of gestation.3–5 Secondly, there is great reliance placed on the use of ultrasound-based fetal measurement reference charts, where individual fetal biometry is compared with predicted values from a normal population. This screening test attempts to assess whether the individual fetus is correctly grown, too large or too small. Serial ultrasound assessments create an individualised growth trajectory for the fetus and are often more clinically useful than a single point measure. Customised fetal growth charts, which take into account maternal and fetal characteristics which may impact growth, and therefore may be better able to differentiate constitutional compared with pathological small fetuses, have been advocated by some but have the potential to undercall growth restriction and, on occasions, falsely reassure.6,7 The choice of fetal biometry reference charts can impact on prenatal management by erroneously mislabelling a fetus as growth restricted, potentially increasing obstetric intervention where none was warranted.8 This poorly recognised phenomenon was recently highlighted in Australia by Elizabeth McCarthy and co-workers where a survey of fellows and trainees of RANZCOG revealed a wide range of ultrasound fetal biometry charts in use throughout Australia.2 The authors correctly highlighted the potential adverse sequelae of using poorly validated or unpublished charts, including false-positive and false-negative diagnoses and practitioner
and patient confusion. It is hoped that the recent Fetal Growth Longitudinal Study publication from the INTERGROWTH-21st Project, which incorporates the introduction of international standards for fetal growth, will provide a reliable reference range to facilitate the recognition of abnormal fetal growth patterns.9 In 2014, the multicentre population-based Fetal Longitudinal Growth Study was published.9 More than 4000 low-risk pregnant women with a singleton fetus from eight countries were recruited and fetal measurements assessed every 5 weeks from 14- to 42-weeks’ gestation. The methodology of this study was meticulous, to overcome issues of quality assurance and sonographer skill. Fetal biometry charts have been produced from this study to represent international standards for fetal growth and size. If these biometry charts of normal fetal growth are adopted internationally, some of the prior issues of variance of ultrasound-based fetal growth assessment founded purely on the reference charts used may be resolved. Thirdly, screening for abnormalities of fetal growth is currently based on maternal perceptions of fetal size, clinical examination (traditionally symphysial fundal height) and selective (targeted) ultrasound assessment of pregnancies considered to be at increased risk of fetal growth disturbances based on maternal risk factors and/or clinical review. The currently available biomarkers are not clinically useful in predicting fetal growth restriction.10 However, in routine clinical practice, the detection of fetal growth aberrations is poor.11,12 This is disturbing, given the increased risk of stillbirth and adverse outcomes in growthrestricted fetuses and the imperative to improve antenatal recognition of the fetus at risk from growth disturbances. In this issue of ANZJOG, an insightful review of fetal growth restriction is presented by Sue Walker and colleagues.13 In particular, this group highlights the failure of umbilical artery Doppler to discriminate the fetus truly at risk in lateonset growth restriction. This important phenomenon is now being increasingly recognised and a shift to the use of tests of centralisation of the fetal circulation is occurring.14 Whilst superficially attractive, the routine use of ultrasound in the third trimester has, to date, not improved perinatal mortality or the detection of small for gestational age fetuses.11,12 In a population-based nonrandomised study in Sweden of >200 000 pregnancies, the use of routine third trimester ultrasound did not appear to reduce perinatal mortality or early neonatal morbidity.12 Clearly, this noncontrolled study has significant limitations but is consistent with the meta-analysis of eight randomised trials involving 27 000 women demonstrating that routine ultrasound in the third trimester in unselected populations does not appear to confer any maternal or fetal benefit.11 Indeed, there was a nonsignificant increase in the caesarean
© 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists The Australian and New Zealand Journal of Obstetrics and Gynaecology
1
Editorial
delivery rate in those women receiving routine third trimester ultrasound (RR1.06, 95% CI 1.00–1.13, P = 0.07), highlighting the potential increases in intervention which may occur with nonselective population screening. At the other extreme of fetal growth is macrosomia. The pregnancy complicated by the large fetus is also at increased risk – both maternal and fetal.15 Recognised maternal risks include genital tract trauma, postpartum haemorrhage and operative delivery. The large fetus is at increased risk of perinatal trauma, hypoxia and neonatal mortality. The prevalence of macrosomia is increasing in many countries, presumably secondary to the rise in maternal obesity and its obstetric consequences.16 Just as with the small fetus, there is poor sensitivity and specificity in the prenatal detection of the macrosomic fetus.3,17 A recent publication in ANZJOG of women screened with ultrasound late in pregnancy demonstrated only a 33% identification of fetuses with a birthweight >4000 g using this technology.17 In this issue of ANZJOG, data are presented on extreme fetal macrosomia, defined as a birthweight >5000 g.18 Affecting 0.4% of deliveries in this Irish cohort, the majority of multiparous women achieved a vaginal birth (86%), substantially lower in nulliparous women (47%), but there was a 14% shoulder dystocia incidence and a postpartum haemorrhage >1000 ml incidence of 6%, highlighting the complications for both the woman and her fetus in this circumstance. Unfortunately, the predictive capacity for fetal macrosomia is poor and all obstetric units should maintain skills in the emergent management of the complications that may occur with these deliveries. Strategies to reduce the incidence of maternal obesity prior to conception, timely recognition and management of gestational diabetes and optimising control of glycaemia in pregestational diabetes are likely to be effective in decreasing fetal macrosomia rates, but difficult to achieve in practice. The accurate determination of both fetal growth in pregnancy and birthweight remains elusive at present, hindering interventions to improve outcomes. Although ultrasound may be a useful tool in identifying abnormal fetal growth, especially the very preterm growth-restricted fetus, it is of lower accuracy than most women and many obstetricians believe. The current inconsistencies in definitions of fetal growth disturbances, suboptimal techniques to identify the fetus with growth abnormalities and broad variations in obstetric management strategies have produced confusion for clinicians. It is hoped that the data from the Fetal Longitudinal Growth Study may provide some consistency in fetal growth assessment as a landing page for future strategies in the identification and management of fetal growth disorders. Jan E. DICKINSON Australian and New Zealand Journal of Obstetrics and Gynaecology, School of Women’s and Infants’ Health, The University of Western Australia, Perth, Western Australia, Australia E-mail: [email protected]
2
References 1 Ioannou C, Talbot K, Ohuma E et al. Systematic review of methodology used in ultrasound studies aimed at creating charts of fetal size. BJOG 2012; 119: 1425–1439. 2 McCarthy EA, Shub A, Walker SP. Is that femur really short? A survey of current and best practice in fetal biometry. Aust N Z J Obstet Gynaecol 2013; 53: 203–206. 3 Haram K, Pirhonen J, Bergsjo P. Suspected big baby: a difficult clinical problem in obstetrics. Acta Obstet Gynecol Scand 2002; 81: 185–194. 4 Boulet SL, Alexander GR, Salihu HM, Pass M. Macrosomic births in the United States: determinants, outcomes and proposed grades of risk. Am J Obstet Gynecol 2003; 188: 1372–1378. 5 American College of Obstetricians and Gynecologists (ACOG). ACOG Practice Bulletin. No. 22. Washington, DC: ACOG, 2000. 6 Gardosi J. Customised assessment of fetal growth potential: implications for perinatal care. Arch Dis Child Fetal Neonatal Ed 2012; 97: F314–F317. 7 Hutcheon JA, Zhang X, Platt RW et al. The case against customised birthweight standards. Paediatr Perinat Epidemiol 2011; 25 (1): 11–16. 8 Salomon LJ, Bernard JP, Duyme M et al. The impact of choice of reference charts and equations on the assessment of fetal biometry. Ultrasound Obstet Gynecol 2005; 25: 559–565. 9 Papageorghiou AT, Ohuma EO, Altman DG et al. International standards for fetal growth based on serial ultrasound measurements: the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project. Lancet 2014; 384: 869–879. 10 Conde-Agudelo A, Papageorghiou AT, Kennedy SH, Villar J. Novel biomarkers for predicting intrauterine Growth restriction: a systematic review and meta-analysis. BJOG 2013; 120: 681–694. 11 Bricker L, Neilson JP, Dowswell T. Routine ultrasound in late pregnancy (after 24 weeks’ gestation). Cochrane Database Syst Rev 2008; 4: CD001451. 12 Sylvan K, Ryding EL, Rydhstroem H. Routine ultrasound screening in the third trimester: a population-based study. Acta Obstet Gynecol Scand 2005; 84: 1154–1158. 13 Macdonald TM, McCarthy EA, Walker SP. Shining light in dark corners: diagnosis and management of late onset fetal growth restriction. Aust N Z J Obstet Gynaecol 2015; 55: 3–10. 14 Morales-Rosello J, Khalil A, Morlando M et al. Changes in fetal Doppler indices as a marker of failure to reach growth potential at term. Ultrasound Obstet Gynecol 2014; 43: 303–310. 15 Ju H, Chadha Y, Donovan T, O’Rourke P. Fetal macrosomia and pregnancy outcomes. Aust N Z J Obstet Gynaecol 2009; 49: 504–509. 16 Dickinson JE. The increasing impact of maternal obesity on obstetric practice. Aust N Z J Obstet Gynaecol 2012; 52: 409–411. 17 Phillips AM, Galdamez AB, Ounpraseuth ST, Magann EF. Estimate of fetal weight by ultrasound within two weeks of delivery in the detection of fetal macrosomia. Aust N Z J Obstet Gynaecol 2014; 54: 441–444. 18 Hehir MP, McHugh AF, Maguire PJ, Mahony R. Extreme macrosomia – Obstetric outcomes and complications in birthweights > 5000g. Aust N Z J Obstet Gynaecol 2015; 55: 42–46.
© 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists
Copyright of Australian & New Zealand Journal of Obstetrics & Gynaecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
DOI: 10.1111/ajo.12320
Editorial
Fetal growth: too big, too little, just right In recognition of the increased short- and long-term complication rates for the extremes of fetal weight, an assessment of fetal size (either clinical and/or sonographic) is routinely performed as a core component of prenatal care. It therefore is disappointing that (a) there is inconsistency in the definitions of fetal growth anomalies, (b) there is currently no internationally accepted standard for assessing fetal growth, (c) available techniques to identify both the macrosomic and the growth-restricted fetus are hounded by poor sensitivity and specificity, and (d) there are few interventions, particularly for the growth-restricted fetus, that modify the intrauterine growth trajectory. Why is the prenatal determination of fetal growth abnormalities so problematic? Firstly, the definition of abnormal fetal growth is imprecise with variation between publications and no currently accepted single international standard for assessing fetal growth. The definition of fetal growth restriction fundamentally represents the failure of a fetus to reach its growth potential; however, definitions range from the third, the fifth to the tenth percentile for any given gestation1 and a broad range of ultrasound fetal growth reference charts is used, both in publications and clinical practice.1,2 Similarly, for fetal macrosomia, the definition varies from an estimated fetal weight >90th percentile for a given gestation or a birthweight >4000– 4500 g independent of gestation.3–5 Secondly, there is great reliance placed on the use of ultrasound-based fetal measurement reference charts, where individual fetal biometry is compared with predicted values from a normal population. This screening test attempts to assess whether the individual fetus is correctly grown, too large or too small. Serial ultrasound assessments create an individualised growth trajectory for the fetus and are often more clinically useful than a single point measure. Customised fetal growth charts, which take into account maternal and fetal characteristics which may impact growth, and therefore may be better able to differentiate constitutional compared with pathological small fetuses, have been advocated by some but have the potential to undercall growth restriction and, on occasions, falsely reassure.6,7 The choice of fetal biometry reference charts can impact on prenatal management by erroneously mislabelling a fetus as growth restricted, potentially increasing obstetric intervention where none was warranted.8 This poorly recognised phenomenon was recently highlighted in Australia by Elizabeth McCarthy and co-workers where a survey of fellows and trainees of RANZCOG revealed a wide range of ultrasound fetal biometry charts in use throughout Australia.2 The authors correctly highlighted the potential adverse sequelae of using poorly validated or unpublished charts, including false-positive and false-negative diagnoses and practitioner
and patient confusion. It is hoped that the recent Fetal Growth Longitudinal Study publication from the INTERGROWTH-21st Project, which incorporates the introduction of international standards for fetal growth, will provide a reliable reference range to facilitate the recognition of abnormal fetal growth patterns.9 In 2014, the multicentre population-based Fetal Longitudinal Growth Study was published.9 More than 4000 low-risk pregnant women with a singleton fetus from eight countries were recruited and fetal measurements assessed every 5 weeks from 14- to 42-weeks’ gestation. The methodology of this study was meticulous, to overcome issues of quality assurance and sonographer skill. Fetal biometry charts have been produced from this study to represent international standards for fetal growth and size. If these biometry charts of normal fetal growth are adopted internationally, some of the prior issues of variance of ultrasound-based fetal growth assessment founded purely on the reference charts used may be resolved. Thirdly, screening for abnormalities of fetal growth is currently based on maternal perceptions of fetal size, clinical examination (traditionally symphysial fundal height) and selective (targeted) ultrasound assessment of pregnancies considered to be at increased risk of fetal growth disturbances based on maternal risk factors and/or clinical review. The currently available biomarkers are not clinically useful in predicting fetal growth restriction.10 However, in routine clinical practice, the detection of fetal growth aberrations is poor.11,12 This is disturbing, given the increased risk of stillbirth and adverse outcomes in growthrestricted fetuses and the imperative to improve antenatal recognition of the fetus at risk from growth disturbances. In this issue of ANZJOG, an insightful review of fetal growth restriction is presented by Sue Walker and colleagues.13 In particular, this group highlights the failure of umbilical artery Doppler to discriminate the fetus truly at risk in lateonset growth restriction. This important phenomenon is now being increasingly recognised and a shift to the use of tests of centralisation of the fetal circulation is occurring.14 Whilst superficially attractive, the routine use of ultrasound in the third trimester has, to date, not improved perinatal mortality or the detection of small for gestational age fetuses.11,12 In a population-based nonrandomised study in Sweden of >200 000 pregnancies, the use of routine third trimester ultrasound did not appear to reduce perinatal mortality or early neonatal morbidity.12 Clearly, this noncontrolled study has significant limitations but is consistent with the meta-analysis of eight randomised trials involving 27 000 women demonstrating that routine ultrasound in the third trimester in unselected populations does not appear to confer any maternal or fetal benefit.11 Indeed, there was a nonsignificant increase in the caesarean
© 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists The Australian and New Zealand Journal of Obstetrics and Gynaecology
1
Editorial
delivery rate in those women receiving routine third trimester ultrasound (RR1.06, 95% CI 1.00–1.13, P = 0.07), highlighting the potential increases in intervention which may occur with nonselective population screening. At the other extreme of fetal growth is macrosomia. The pregnancy complicated by the large fetus is also at increased risk – both maternal and fetal.15 Recognised maternal risks include genital tract trauma, postpartum haemorrhage and operative delivery. The large fetus is at increased risk of perinatal trauma, hypoxia and neonatal mortality. The prevalence of macrosomia is increasing in many countries, presumably secondary to the rise in maternal obesity and its obstetric consequences.16 Just as with the small fetus, there is poor sensitivity and specificity in the prenatal detection of the macrosomic fetus.3,17 A recent publication in ANZJOG of women screened with ultrasound late in pregnancy demonstrated only a 33% identification of fetuses with a birthweight >4000 g using this technology.17 In this issue of ANZJOG, data are presented on extreme fetal macrosomia, defined as a birthweight >5000 g.18 Affecting 0.4% of deliveries in this Irish cohort, the majority of multiparous women achieved a vaginal birth (86%), substantially lower in nulliparous women (47%), but there was a 14% shoulder dystocia incidence and a postpartum haemorrhage >1000 ml incidence of 6%, highlighting the complications for both the woman and her fetus in this circumstance. Unfortunately, the predictive capacity for fetal macrosomia is poor and all obstetric units should maintain skills in the emergent management of the complications that may occur with these deliveries. Strategies to reduce the incidence of maternal obesity prior to conception, timely recognition and management of gestational diabetes and optimising control of glycaemia in pregestational diabetes are likely to be effective in decreasing fetal macrosomia rates, but difficult to achieve in practice. The accurate determination of both fetal growth in pregnancy and birthweight remains elusive at present, hindering interventions to improve outcomes. Although ultrasound may be a useful tool in identifying abnormal fetal growth, especially the very preterm growth-restricted fetus, it is of lower accuracy than most women and many obstetricians believe. The current inconsistencies in definitions of fetal growth disturbances, suboptimal techniques to identify the fetus with growth abnormalities and broad variations in obstetric management strategies have produced confusion for clinicians. It is hoped that the data from the Fetal Longitudinal Growth Study may provide some consistency in fetal growth assessment as a landing page for future strategies in the identification and management of fetal growth disorders. Jan E. DICKINSON Australian and New Zealand Journal of Obstetrics and Gynaecology, School of Women’s and Infants’ Health, The University of Western Australia, Perth, Western Australia, Australia E-mail: [email protected]
2
References 1 Ioannou C, Talbot K, Ohuma E et al. Systematic review of methodology used in ultrasound studies aimed at creating charts of fetal size. BJOG 2012; 119: 1425–1439. 2 McCarthy EA, Shub A, Walker SP. Is that femur really short? A survey of current and best practice in fetal biometry. Aust N Z J Obstet Gynaecol 2013; 53: 203–206. 3 Haram K, Pirhonen J, Bergsjo P. Suspected big baby: a difficult clinical problem in obstetrics. Acta Obstet Gynecol Scand 2002; 81: 185–194. 4 Boulet SL, Alexander GR, Salihu HM, Pass M. Macrosomic births in the United States: determinants, outcomes and proposed grades of risk. Am J Obstet Gynecol 2003; 188: 1372–1378. 5 American College of Obstetricians and Gynecologists (ACOG). ACOG Practice Bulletin. No. 22. Washington, DC: ACOG, 2000. 6 Gardosi J. Customised assessment of fetal growth potential: implications for perinatal care. Arch Dis Child Fetal Neonatal Ed 2012; 97: F314–F317. 7 Hutcheon JA, Zhang X, Platt RW et al. The case against customised birthweight standards. Paediatr Perinat Epidemiol 2011; 25 (1): 11–16. 8 Salomon LJ, Bernard JP, Duyme M et al. The impact of choice of reference charts and equations on the assessment of fetal biometry. Ultrasound Obstet Gynecol 2005; 25: 559–565. 9 Papageorghiou AT, Ohuma EO, Altman DG et al. International standards for fetal growth based on serial ultrasound measurements: the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project. Lancet 2014; 384: 869–879. 10 Conde-Agudelo A, Papageorghiou AT, Kennedy SH, Villar J. Novel biomarkers for predicting intrauterine Growth restriction: a systematic review and meta-analysis. BJOG 2013; 120: 681–694. 11 Bricker L, Neilson JP, Dowswell T. Routine ultrasound in late pregnancy (after 24 weeks’ gestation). Cochrane Database Syst Rev 2008; 4: CD001451. 12 Sylvan K, Ryding EL, Rydhstroem H. Routine ultrasound screening in the third trimester: a population-based study. Acta Obstet Gynecol Scand 2005; 84: 1154–1158. 13 Macdonald TM, McCarthy EA, Walker SP. Shining light in dark corners: diagnosis and management of late onset fetal growth restriction. Aust N Z J Obstet Gynaecol 2015; 55: 3–10. 14 Morales-Rosello J, Khalil A, Morlando M et al. Changes in fetal Doppler indices as a marker of failure to reach growth potential at term. Ultrasound Obstet Gynecol 2014; 43: 303–310. 15 Ju H, Chadha Y, Donovan T, O’Rourke P. Fetal macrosomia and pregnancy outcomes. Aust N Z J Obstet Gynaecol 2009; 49: 504–509. 16 Dickinson JE. The increasing impact of maternal obesity on obstetric practice. Aust N Z J Obstet Gynaecol 2012; 52: 409–411. 17 Phillips AM, Galdamez AB, Ounpraseuth ST, Magann EF. Estimate of fetal weight by ultrasound within two weeks of delivery in the detection of fetal macrosomia. Aust N Z J Obstet Gynaecol 2014; 54: 441–444. 18 Hehir MP, McHugh AF, Maguire PJ, Mahony R. Extreme macrosomia – Obstetric outcomes and complications in birthweights > 5000g. Aust N Z J Obstet Gynaecol 2015; 55: 42–46.
© 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists
Copyright of Australian & New Zealand Journal of Obstetrics & Gynaecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
