intrauterine growth restriction
Post on 12-Jan-2016
Embed Size (px)
DESCRIPTIONIntrauterine growth restriction. An evidence based approach. Introduction and background. IUGR remains a challenging problem for both the obstetrician and pediatrician. - PowerPoint PPT Presentation
Introduction and background IUGR remains a challenging problem for both the obstetrician and pediatrician. The ability to diagnose the disorder and understand its pathophysiology still outpaces the ability to prevent its complications..
Introduction and background. Fetal growth restriction is the second leading cause of perinatal morbidity and mortality. The incidence of intrauterine growth restriction (IUGR) is estimated to be approximately 5 percent in the general obstetric population
PERINATAL IMPLICATIONS IUGR causes a spectrum of perinatal complications, includingfetal deaths, prematurity, neonatal death, fetal compromise in labor, neonatal morbidity, induction of labor, and cesarean delivery.Neonates with IUGR who survive the intrauterine experience are at increased risk for impaired neurodevelopment, and possibly type 2 diabetes and hypertension in adult life.
DEFINITIONS The term IUGR has changed from intrauterine growth retardation to the more current term, intrauterine growth restriction.. IUGR:- a fetus is unable to grow to its genetically determined potential size to a degree that may affect the health of the fetus.
DEFINITIONSSGA :-refer to a fetus that has failed to achieve a specific biometric or estimated weight threshold by a specific gestational age.. The commonly used threshold is the tenth centile for abdominal circumference and estimated birthweight
- DEFINITIONS5070% of fetuses with a birthweight below tenth centile for gestational age are constitutionally small, and the lower the centile for defining SGA, the higher the likelihood of FGRNot all fetuses who are SGA (
Symmetric and Asymmetric IUGR. Symmetric growth restriction implies a fetus whose entire body is proportionally small.Asymmetric growth restriction implies a fetus who is undernourished and is directing most of its energy to maintaining growth of vital organs, such as the brain and heart, at the expense of the liver, muscle and fat. This type of growth restriction is usually the result of placental insufficiency.
Symmetric and Asymmetric IUGRInvestigators have differed on the importance of this differentiation in the diagnosis and management But recently. The symmetrically grown infants who were SGA had outcomes very similar to the infants who were AGA. E-medicine May 2002
maternal causes Possible maternal causes of IUGR :-Chronic hypertension Pregnancy-associated hypertension Cyanotic heart disease Class F or higher diabetes Hemoglobinopathies Autoimmune disease Protein-calorie malnutrition Smoking Substance abuse Uterine malformations Thrombophilia
Fetal causesPossible causes of IUGR related to the placenta and/or umbilical cord :-Multiple gestation Twin-to-twin transfusion Abnormal cord insertion Placental abnormality Chronic abruption Placenta previa Cord anomaliesIdentifying a cause may not be possible in as many as 40% of cases
DiagnosisFour important issues need to be considered :1- most measurements require an accurate estimation of gestation as a prerequisite2-most tests attempt to diagnose SGA fetuses rather than growth-restricted fetuses3-most studies use a one-off measurement (size) to predict SGA while there is evidence that it is the trend (growth) that is of more value in predicting poor fetal outcome4- no attention is made for important prognostic factors for SGA, such as maternal height, weight, ethnicity, parity and fetal gender
It should also be noted that, although an individual test alone may not be predictive of SGA or FGR, a composite of abnormal results such as an ultrasonically small fetus with reduced liquor or abnormal uterine artery Doppler may indicate pathology.
Diagnosis. A distinction needs to be made between biometric tests (tests to measure size) and biophysical tests (tests to assess fetal wellbeing . the diagnosis of SGA would rely on biometric tests while abnormal biophysical tests are more indicative of FGR than SGA.
Diagnosis 1- Abdominal palpation Grade C . Abdominal palpation has limited diagnostic accuracy to predict a SGA fetus.RCOG November 2002
Diagnosis 2- Fundal heightGrade BSymphyseal fundal height (SFH) measurement has limited diagnostic accuracy to predict an SGA neonate.Although early studies reported high sensitivity and specificity , a large study of 2941 women found the sensitivity and specificity to be 27% and 88%, respectively. Serial measurements may improve sensitivity and specificity
RCOG November 2002
Diagnosis 2- Fundal heightGrade BA customised fundal height chart improves accuracy to predict a SGA fetus.A customised SFH chart is adjusted for physiological variables such as maternal height, weight, parity and ethnic group. Use of such charts was found to result in improvement in sensitivity .RCOG November 2002
Diagnosis 3- Ultrasound biometryGradeBA-Abdominal circumference and estimated fetal weight to diagnose SGA.They are the most accurate diagnostic measurements to predict SGA. In high-risk women, AC at less than the tenth centile has sensitivities of 72.994.5% and specificities of 50.683.8% in the prediction of fetuses with birthweight at less than the tenth centile.
RCOG November 2002
Diagnosis 3- Ultrasound biometryGrade B B-Customised ultrasound charts.Customised ultrasound EFW charts that are adjusted for important independent physiological variables, such as maternal weight, maternal height, ethnic group and parity, have better sensitivities for identifying SGA fetuses , FGR, have lower false-positive rates and are predictive of poor perinatal events.RCOG November 2002
Diagnosis 3- Ultrasound biometryGrade B C- Growth velocity in addition to size.Serial measurements of AC and EFW (growth velocities) are superior to single estimates of AC or EFW in the prediction of FGR and predicting poor perinatal outcome.However, use of fetal growth alone to diagnose growth restriction (especially when the interval between the scan is less than two weeks) can lead to high numbers of false positives.
RCOG November 2002
Diagnosis 3- Ultrasound biometryRatio measures, such as head to abdominal circumference (HC/AC) and femoral length to abdominal circumference (FL/AC) ratios are poorer than AC or EFW alone in predicting SGA.A systematic review in the Cochrane Database of Systematic Reviews has shown that routine ultrasound after 24 weeks in low-risk pregnancy does not improve perinatal outcomeCochrane library Evidencelevel Ia
Diagnosis 4- Biophysical tests
All biophysical tests, including amniotic fluid volume (AFV), Doppler, cardiotocography and biophysical scoring, are poor at diagnosing a small or growth-restricted fetus.RCOG November 2002
Diagnosis 4- Biophysical testsGrade B.AFV has minimal value in diagnosing FGR Despite the positive association between AFV and neonatal morphometry, the likelihood ratios remain low. For amniotic fluid index (AFI), a positive test result has a likelihood ratio (LR) of 2.4 for predicting skinfold thickness below the tenth centileSerial measurements of AFI have similarly disappointing results RCOG November 2002
Diagnosis 4- Biophysical tests Grade A.Uterine artery Doppler has limited use in predicting FGR.A systematic review with meta-analysis published in 2000 found that uterine artery Doppler had limited accuracy in predicting FGR and perinatal deathAbnormal uterine artery suggest a maternal cause for the growth restriction where as normal uterine artery Doppler studies suggest that a fetal causeRCOG November 2002
managementAt this point, the only reasonable goals in the treatment of IUGR are to deliver the most mature fetus in the best condition possible with minimal risk to the mother. Such a goal requires the use of antenatal testing in hope of identifying the fetus with IUGR before it becomes acidotic.
1- Assessment for chromosomal defectsWhen a small fetus is diagnosed, assess for risk of chromosomal defects.Up to 19% of fetuses with an AC and EFW less than the fifth centile may have chromosomal defectsThe risk is higher when growth restriction is associated with structural abnormalities, a normal liquor volume or a normal uterine or umbilical artery Doppler. Therefore, all growth-restricted fetuses need an ultrasound anatomical survey as a minimum. It may also be appropriate to offer karyotyping.
2- Surveillance of the small fetus (umbilical artery Doppler )Grade AUse umbilical artery Doppler as the primary surveillance tool.A systematic review with meta-analysis has provided evidence that the use of umbilical artery Doppler to monitor high-risk fetuses reduces perinatal morbidity and mortality. In addition, there was a significant reduction in the number of antenatal admissions and inductions of labourRCOG November 2002
umbilical artery Doppler In normal pregnancy, there is a progressive increase in end-diastolic velocity due to growth and dilatation of the umbilical circulation. The resistance index therefore falls. A resistance index > 0.72 is outside the normal limits from 26 weeks gestation onwards. In some pregnancies with fetal growth restriction and/or preeclampsia, there is a reduction in the diastolic velocity and in severe cases, there is absent or reversed end diastolic velocity.
2- Surveillance of the small fetus (umbilical artery Doppler ). A study comparing fetal heart-rate monitoring, biophysical profile and umbilical artery Doppler found that only umbilical artery Doppler had value in predicting poor perinatal outcomes in SGAScreening a low-risk or unselected population by umbilical ar