Diagnostic Imaging Pathways - Fetal Wellbeing (Assessment)
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This pathway provides guidance on the imaging assessment of pregnant patients for fetal well-being in the third trimester.
Date reviewed: October 2013
Date of next review: 2017/2018
Published: November 2013
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| SYMBOL | RRL | EFFECTIVE DOSE RANGE |
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Images
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| 1a |  |
Intrauterine Growth Restriction Image 1a,b,c (Ultrasound, 33 weeks gestation): The fetus is in a cephalic presentation. The placenta is situated on the posterior uterine wall, clear of the cervix. Measurements: Biparietal diameter 78mm, Head circumference 283mm, Abdominal circumference 266mm, Femur length 58mm. Estimated fetal weight 1625g +/- 237g. Amniotic fluid volume is normal (Amniotic Fluid Index = 12cm).
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| 1b |  |
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| 1c |  |
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| 1d |  |
Image 1d (Fetal Biometry Chart, 33 weeks gestation): The above measurements are all below the 3rd percentile. |
Teaching Points
Teaching Points
- Routine ultrasound in the third trimester is not indicated. However, there are a number of maternal, fetal and pregnancy related indications for an ultrasound examination at this time. These include 4
- Pregnancy induced hypertension/pre-eclampsia
- Chronic renal disease and hypertension
- Maternal diabetes mellitus, pregnancy induced diabetes mellitus
- Maternal vascular disorders
- Suspected or previous history of IUGR
- Previous history of intrauterine fetal death
- Previous history of abruption
- Multiple pregnancy
- Clinical polyhydramnios or oligohydramnios
- Review of fetal anomaly
- Malpresentation
- Planned vaginal delivery of breech presentation
- Palpates small for dates
- Advanced maternal age (>35 years)
- Umbilical artery Doppler studies in high risk populations can help reduce perinatal mortality. Consider results in conjunction with ultrasound and other Doppler studies of the MCA, uterine artery and ductus venosus
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Assessment of Fetal Wellbeing in the Third Trimester
- Routine conventional or Doppler ultrasound in the third trimester in low-risk or unselected populations has not been demonstrated to be beneficial to either mother or baby or cost-effective 5-7
- Factors that may impact on fetal growth and wellbeing are indications for an ultrasound examination in the third trimester. These include 4
- Pregnancy induced hypertension/pre-eclampsia
- Chronic renal disease and hypertension
- Maternal diabetes mellitus, pregnancy induced diabetes mellitus
- Maternal vascular disorders
- Suspected or previous history of IUGR
- Previous history of intrauterine fetal death
- Previous history of abruption
- Multiple pregnancy
- Clinical polyhydramnios or oligohydramnios
- Review of fetal anomaly
- Malpresentation
- Planned vaginal delivery of breech presentation
- Palpates small for dates
- Advanced maternal age (>35 years)
- Macrosomia describes a large fetus, with an estimated fetal weight greater than the 90th percentile after correcting for sex and ethnicity, or greater than 4500gm. This condition is associated with increased fetal and neonatal morbidity and mortality. Most complications are related to delivery, including shoulder dystocia and birth trauma. Macrosomia associated with maternal diabetes carries a higher risk of intrauterine death. Close monitoring of fetal weight can be used to determine the optimal time for delivery 4
- Small for gestational age (SGA) refers to a fetus with an estimated fetal weight (EFW) or abdominal circumference below the 10th percentile 8
- Intrauterine growth restriction (IUGR) refers to a fetus with an estimated fetal weight below the 10th percentile corrected for sex and ethnicity and implies a pathological restriction of the genetic growth potential. 8 There may be features of chronic hypoxia and/or malnutrition, but a consensus does not exist for the definition of IUGR. It is associated with adverse fetal outcomes including acidosis, stillbirth, oligohydramnios and low-birth weight; and adverse events during labour including fetal distress in labour 4
us
Ultrasound
- Conventional and Doppler ultrasonography are used to assess fetal wellbeing through the following parameters 3,9
- Fetal biometry: including estimated fetal weight (EFW), abdominal circumference (AC), head circumference, femur length and assessment of the placenta and umbilical cord. AC is the most sensitive measurement for assessing fetal wellbeing
- Biophysical profile (BPP): fetal heart rate, breathing, movements, tone and amniotic fluid volume
- Umbilical artery Doppler ultrasound with calculation of the systolic to diastolic (S/D) ratio which can be related to gestational age on a nomogram
- Percentile charts are used to assess the estimated fetal weight for age. Normal values are arbitrarily chosen as between the 10th and 90th percentiles
- When there is placental insufficiency, progressive feto-placental circulation haemodynamic changes occur that can be detected on umbilical artery Doppler studies, aided by Doppler studies of the middle cerebral artery (MCA), uterine artery and ductus venosus and umbilical vein 3,11-13
- Doppler indices from the umbilical artery start to increase (with reduced end diastolic flow and increased S/D ratio) when functioning of the placental vascular tree is impaired 12
- There is preferential flow to the brain (“brain sparing effect”), heart and adrenal glands, with increased cerebral diastolic flow and cerebral vasodilation leading to decreased MCA Doppler indices,14 while aortic blood flow resistance increases 12
- Late Doppler changes include absent or reversed end diastolic flow in the umbilical artery and increase in the resistance of venous blood flow in the ductus venosus and inferior vena cava 12
- Systematic reviews of conventional or Doppler ultrasound use have not yet demonstrated a benefit in the routine screening of low-risk or unselected patients 6,7
- In high risk or selected populations, umbilical artery Doppler can predict mortality and risk of fetal compromise, and help guide management and timing of delivery 15. Use of fetal and umbilical artery Doppler ultrasound surveillance reduces the risk of perinatal death and obstetric intervention 12,16
- Studies of MCA Doppler are conflicting. A recent meta-analysis found MCA Doppler to have a limited predictive accuracy for perinatal wellbeing 14
- It may be useful after 32 weeks gestation where umbilical artery Doppler is normal. In one study MCA pulsatility index <5th centile was predictive of emergency caesarean section and neonatal metabolic acidosis 17
- Ductus venosus Doppler showed moderate predictive accuracy for perinatal mortality in high risk fetuses with placental insufficiency 18
- If IUGR is diagnosed and there are no indications for immediate delivery, fetal monitoring is appropriate. 19,20 This usually consists of serial ultrasound (biophysical profile, S/D ratios, and assessment of fetal growth) and cardiotocography (CTG). Compared to serial CTG, serial umbilical artery Doppler significantly reduces the need for emergency caesarean deliveries for fetal distress in-utero 21
References
References
Date of literature search: July 2013
The search methodology is available on request. Email
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- Rossi AC, Prefumo F. Perinatal outcomes of isolated oligohydramnios at term and post-term pregnancy: a systematic review of literature with meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2013;169(2):149-54. (Level III evidence)
- Zhang J, Troendle J, Meikle S, Klebanoff MA, Rayburn WF. Isolated oligohydramnios is not associated with adverse perinatal outcomes. BJOG. 2004;111(3):220-5. (Level II evidence)
- Lausman A, McCarthy FP, Walker M, Kingdom J. Screening, diagnosis and management of intrauterine growth restriction. J Obstet Gynaecol Can. 2012;34(1):17-28. (Review article)
- Nyberg D, Abuhamad A, Ville Y. Ultrasound assessment of abnormal fetal growth. Semin Perinatol. 2004;28(1):3-22. (Review article)
- Sylvan K, Ryding EL, Rydhstroem H. Routine ultrasound screening in the third trimester: a population-based study. Acta Obstet Gynecol Scand. 2005;84(12):1154-8. (Level II evidence)
- Bricker L, Neilson JP, Dowswell T. Routine ultrasound in late pregnancy (after 24 weeks' gestation). Cochrane Database Syst Rev. 2008(4):CD001451. (Level I evidence)
- Alfirevic Z, Stampalija T, Gyte GM. Fetal and umbilical Doppler ultrasound in normal pregnancy. Cochrane Database Syst Rev. 2010 (8):CD001450. (Level I/II evidence)
- Royal College of Obstetricians and Gynaecologists. Green-top guideline No. 31: The investigation and management of the small-for-gestational-age fetus. 2013 [cited 2013 July 1]. (Evidence based guideline). View the reference
- Harman C, Baschat A. Comprehensive assessment of fetal wellbeing: which Doppler tests should be performed? Curr Opin Obstet Gynecol. 2003;15(2):147-57. (Review article)
- Australasian Society for Ultrasound in Medicine. Guidelines for the performance of third trimester ultrasound. ASUM guidelines; 1999. (Position statement)
- Harman CR, Baschat AA. Arterial and venous Dopplers in IUGR. Clin Obstet Gynecol. 2003;46(4):931-46. (Review article)
- Alfirevic Z, Stampalija T, Gyte GM. Fetal and umbilical Doppler ultrasound in high-risk pregnancies. Cochrane Database Syst Rev. 2010 (1):CD007529. (Level I evidence)
- Cosmi E, Ambrosini G, D'Antona D, Saccardi C, Mari G. Doppler, cardiotocography, and biophysical profile changes in growth-restricted fetuses. Obstet Gynecol. 2005;106(6):1240-5. (Level III evidence)
- Morris RK, Say R, Robson SC, Kleijnen J, Khan KS. Systematic review and meta-analysis of middle cerebral artery Doppler to predict perinatal wellbeing. Eur J Obstet Gynecol Reprod Biol. 2012;165(2):141-55. (Level II evidence)
- Morris RK, Malin G, Robson SC, Kleijnen J, Zamora J, Khan KS. Fetal umbilical artery Doppler to predict compromise of fetal/neonatal wellbeing in a high-risk population: systematic review and bivariate meta-analysis. Ultrasound Obstet Gynecol. 2011;37(2):135-42. (Level I/II evidence)
- Alfirevic Z, Neilson JP. Doppler ultrasonography in high-risk pregnancies: systematic review with meta-analysis. Am J Obstet Gynecol. 1995;172(5):1379-87. (Level II evidence)
- Severi FM, Bocchi C, Visentin A, Falco P, Cobellis L, Florio P, et al. Uterine and fetal cerebral Doppler predict the outcome of third-trimester small-for-gestational age fetuses with normal umbilical artery Doppler. Ultrasound Obstet Gynecol. 2002;19(3):225-8. (Level III evidence)
- Morris RK, Selman TJ, Verma M, Robson SC, Kleijnen J, Khan KS. Systematic review and meta-analysis of the test accuracy of ductus venosus Doppler to predict compromise of fetal/neonatal wellbeing in high risk pregnancies with placental insufficiency. Eur J Obstet Gynecol Reprod Biol. 2010;152(1):3-12. (Level I/II evidence)
- Thornton JG, Hornbuckle J, Vail A, Spiegelhalter DJ, Levene M. Infant wellbeing at 2 years of age in the Growth Restriction Intervention Trial (GRIT): multicentred randomised controlled trial. Lancet. 2004;364(9433):513-20. (Level II evidence)
- Walker DM, Marlow N, Upstone L, Gross H, Hornbuckle J, Vail A, et al. The growth restriction intervention trial: long-term outcomes in a randomized trial of timing of delivery in fetal growth restriction. Am J Obstet Gynecol. 2011;204(1):34 e1-9. (Level II evidence)
- Williams KP, Farquharson DF, Bebbington M, Danscreau J, Galerneau F, Wilson RD, et al. Screening for fetal well-being in a high-risk pregnant population comparing the nonstress test with umbilical artery Doppler velocimetry: a randomized controlled clinical trial. Am J Obstet Gynecol. 2003;188(5):1366-71. (Level II evidence)
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