Management of Fetal Growth Restriction

Definition and Diagnosis

• The American College of Obstetricians and Gynecologists defines fetal growth restriction (FGR) as a fetus with an estimated weight below the 10th percentile for gestational age 1, 2
• Fetal growth restriction occurs in up to 10% of pregnancies and is a leading cause of infant morbidity and mortality 2, 3
• The fetal death rate is approximately 1.5% in fetuses with weight below the 10th percentile, doubling the rate in fetuses with normal growth 3

Initial Evaluation

• The American College of Obstetricians and Gynecologists recommends prenatal diagnostic testing with chromosomal microarray analysis when unexplained isolated FGR is diagnosed before 32 weeks of gestation 1
• The American College of Obstetricians and Gynecologists does not recommend routine screening for toxoplasmosis, rubella, or herpes in pregnancies with FGR in the absence of other risk factors 1
• The American College of Obstetricians and Gynecologists recommends PCR for cytomegalovirus in women with unexplained FGR who choose diagnostic testing with amniocentesis 1

Fetal Surveillance

Doppler Evaluation

• Once FGR is diagnosed, serial Doppler evaluation of the umbilical artery should be performed to detect deterioration 1, 4, 2
• With decreased end-diastolic flow or severe FGR (estimated fetal weight less than the 3rd percentile), weekly Doppler evaluation of the umbilical artery is suggested 1, 4
• Doppler evaluation 2-3 times a week is recommended when absent end-diastolic flow is detected in the umbilical artery 1, 2
• In cases of reversed end-diastolic flow, hospitalization, antenatal corticosteroid administration, and intensified surveillance with cardiotocography at least 1-2 times a day are suggested 1, 4

Cardiotocography Monitoring

• Weekly cardiotocography tests are suggested after viability for FGR without absent or reversed end-diastolic flow 1, 4
• The frequency of cardiotocography should be increased when FGR is complicated by absent or reversed end-diastolic flow or other comorbidities 1, 2

Timing of Delivery

• The American College of Obstetricians and Gynecologists recommends delivery at 37 weeks of gestation in pregnancies with FGR and abnormal umbilical artery Doppler waveforms or severe FGR with estimated fetal weight less than the 3rd percentile 1, 4, 2
• Delivery is recommended at 33-34 weeks of gestation for pregnancies with FGR and absent end-diastolic flow 1, 2
• Delivery is recommended at 30-32 weeks of gestation for pregnancies with FGR and reversed end-diastolic flow 1, 4, 2

Route of Delivery

• For pregnancies with FGR complicated by absent or reversed end-diastolic flow, cesarean delivery should be considered based on the complete clinical scenario 1, 2

Perinatal Interventions

• The American College of Obstetricians and Gynecologists recommends the use of antenatal corticosteroids if delivery is anticipated before 33 6/7 weeks of gestation or for pregnancies between 34 0/7 and 36 6/7 weeks of gestation in women without contraindications with a risk of preterm birth within 7 days 1, 2
• The American College of Obstetricians and Gynecologists recommends intrapartum magnesium sulfate for fetal and neonatal neuroprotection for women with pregnancies less than 32 weeks of gestation 1, 2

Special Considerations

• Fetal growth evaluation should be performed at an interval of no less than 2 weeks, with evaluations every 3-4 weeks being more reliable due to the inherent error in fetal biometry 5, 6
• The volume of amniotic fluid is an important indicator of chronic fetal well-being 5, 6
• The biophysical profile is primarily an assessment of immediate fetal well-being 5, 6

Fetal Growth Restriction and Normal Heart Rate Patterns

Introduction to Fetal Growth Restriction

• The American College of Obstetricians and Gynecologists recommends that normal fetal heart rate testing does not exclude intrauterine growth restriction (IUGR) and should never be used as the sole surveillance method in these high-risk pregnancies 7, 8, 9

Understanding Fetal Heart Rate Patterns

• Early or compensated IUGR typically maintains normal heart rate patterns, normal heart rate variability, and reactive nonstress tests (NSTs) while the fetus is still adapting to chronic hypoxemia through redistribution of blood flow 7, 8
• Heart rate changes occur late in the deterioration sequence—abnormal heart rate patterns (loss of variability, non-reactive NST) typically appear only after significant vascular changes are already present on Doppler studies 10, 9

Surveillance and Monitoring

• The American College of Obstetricians and Gynecologists recommends umbilical artery Doppler as the primary surveillance tool for IUGR, not heart rate monitoring alone 7, 8, 9
• Umbilical artery Doppler should be performed weekly once IUGR is diagnosed, as it detects placental dysfunction before heart rate changes emerge 7, 9
• Doppler abnormalities progress in a predictable sequence: increased umbilical artery resistance → absent end-diastolic flow → reversed end-diastolic flow → venous Doppler changes → finally, abnormal heart rate patterns 10, 9

Management Algorithm

• If umbilical artery Doppler is normal, continue weekly Doppler surveillance and weekly nonstress test (NST) or biophysical profile (BPP) 7, 9
• If umbilical artery shows decreased diastolic flow (but heart rate normal), increase to weekly Doppler and deliver at 37 weeks regardless of normal heart rate 11
• If absent end-diastolic flow (even with normal heart rate), deliver at 33-34 weeks regardless of reassuring heart rate patterns 11
• If reversed end-diastolic flow (even with normal heart rate), deliver at 30-32 weeks regardless of heart rate status 11

Intrapartum Considerations

• IUGR fetuses with normal antepartum heart rate patterns require continuous electronic fetal monitoring during labor 11
• Studies report 75-95% of IUGR pregnancies with absent/reversed end-diastolic flow require cesarean delivery for intrapartum heart rate abnormalities, even when antepartum testing was reassuring 11

Management of Intrauterine Growth Restriction

Surveillance Protocol

• The American College of Obstetricians and Gynecologists recommends initiating weekly umbilical artery Doppler studies immediately upon IUGR diagnosis, as this is the only surveillance modality with Level I evidence showing a 29% reduction in perinatal mortality (RR 0.71, 95% CI 0.52-0.98) 12, 13
• Weekly cardiotocography testing (nonstress test or biophysical profile) should be added after viability for IUGR without absent or reversed end-diastolic velocity, as the combination of ultrasound and cardiotographic surveillance improves outcomes compared to either alone 14, 14
• Increase Doppler surveillance to 2-3 times per week when IUGR is complicated by oligohydramnios, absent end-diastolic flow, or reversed end-diastolic flow 12, 14

Delivery Timing Algorithm

• Deliver at 38-39 weeks of gestation when estimated fetal weight is between the 3rd and 10th percentile with normal Doppler findings, and continue weekly Doppler and weekly cardiotocography until delivery 13, 14, 13
• Deliver at 37 weeks of gestation or when severe IUGR is present (estimated fetal weight less than the 3rd percentile), and maintain weekly Doppler surveillance and increase cardiotocography frequency 13, 14
• Deliver at 33-34 weeks of gestation as long as fetal surveillance remains reassuring when absent end-diastolic flow is present, and increase Doppler surveillance to 2-3 times weekly and perform cardiotocography twice weekly or more often 13, 12, 14
• Deliver at 30-32 weeks of gestation as long as fetal surveillance remains reassuring when reversed end-diastolic flow is present 13

Antenatal Interventions

• Administer antenatal corticosteroids if absent or reversed end-diastolic flow is noted at less than 34 weeks (Level A recommendation), and provide close observation for 48-72 hours after corticosteroid administration 13, 13
• Administer intrapartum magnesium sulfate for fetal and neonatal neuroprotection for pregnancies less than 32 weeks of gestation (GRADE 1A recommendation)

Mode of Delivery Considerations

• Do not use Doppler of any vessel as a screening tool for identifying pregnancies that will subsequently be complicated by IUGR, as standards are lacking for study technique, gestational age at testing, and criteria for abnormal results 13, 15

Combined Serial Ultrasound and Umbilical Artery Doppler Surveillance Improves Outcomes in Pregnancies After Prior IUGR

Evidence Supporting Combined Modalities

• The combination of serial growth ultrasounds and umbilical artery Doppler studies provides complementary information on fetal size and placental function, leading to significantly improved perinatal outcomes in women with a history of intra‑uterine growth restriction (IUGR). 16

Risk Assessment in Women with Prior IUGR

• A prior delivery of a term infant weighing 1.6 kg (≈ < 3rd percentile) indicates a markedly increased risk for recurrent growth restriction in the subsequent pregnancy. 17
• Serial ultrasound growth assessment identifies whether the fetus remains within an appropriate percentile range or shows declining growth velocity, prompting intensified surveillance when abnormal trends are detected. 18

Umbilical Artery Doppler Evidence

• Umbilical artery Doppler is the only surveillance modality with Level I evidence showing a 29 % reduction in perinatal mortality in high‑risk pregnancies (relative risk 0.71; 95 % CI 0.52–0.98). 16
• Doppler waveforms differentiate a constitutionally small but healthy fetus from a hypoxic, growth‑restricted fetus with placental insufficiency, thereby reducing unnecessary interventions while identifying fetuses that require urgent management. 16
• Once IUGR is suspected or confirmed (estimated fetal weight < 10th percentile), weekly umbilical artery Doppler evaluation should be started immediately, as it detects placental dysfunction before fetal heart‑rate changes appear. 16

Surveillance Protocol

Initial Assessment (≈ 26–28 weeks)

• Begin serial growth ultrasounds every 3–4 weeks to establish the fetal growth trajectory; surveillance is indicated when estimated fetal weight falls below the 10th percentile. 16
• Initiate weekly umbilical artery Doppler studies as soon as IUGR is suspected (estimated fetal weight < 10th percentile). 16

Ongoing Monitoring When Growth Restriction Is Detected

• Continue weekly Doppler assessments while forward end‑diastolic flow persists with normal or decreased diastolic flow. 16
• Increase Doppler frequency to 2–3 times per week if absent end‑diastolic flow or oligohydramnios develops. 16

Delivery Timing Recommendations

• Absent end‑diastolic flow: Plan delivery at 33–34 weeks gestation, administer antenatal corticosteroids, and maintain intensified surveillance (Doppler 2–3 times weekly). 16
• Reversed end‑diastolic flow: Plan delivery at 30–32 weeks gestation, admit for hospitalization, give corticosteroids, and perform cardiotocography 1–2 times daily. 16

Limitations of Antenatal Testing

• No antenatal test, including Doppler or fetal heart‑rate monitoring, can predict stillbirth caused by acute events such as placental abruption or cord accidents; therefore, continuous surveillance throughout pregnancy remains essential. 18

Surveillance and Delivery Guidelines for Pregnancies with Prior Intrauterine Growth Restriction

Initial Surveillance Protocol

Monitoring Adjustments When Abnormal Findings Appear

Delivery Timing Based on Combined Growth and Doppler Data

Role of the Biophysical Profile (BPP)

Integrated Management Algorithm

Guideline Recommendations for Management of Fetal Growth Restriction

Prevention Strategies

• Low‑dose aspirin (100–150 mg daily) initiated before 16 weeks gestation lowers the incidence of fetal growth restriction in women with prior preeclampsia, prior FGR, or multiple risk factors. 21
• Smoking cessation at any point during pregnancy is the only other modifiable intervention shown to reduce the risk of fetal growth restriction. 21

Surveillance Protocol After Diagnosis

Umbilical Artery Doppler Monitoring

• Perform umbilical artery Doppler assessment immediately after FGR diagnosis; normal Doppler results warrant repeat scans every 2 weeks. 22
• If decreased end‑diastolic velocity or severe FGR (estimated fetal weight < 3rd percentile) is detected, repeat Doppler weekly. 22
• When absent end‑diastolic velocity (AEDV) is present, increase Doppler frequency to 2–3 times per week. 22

Cardiotocography (NST/BPP)

• Conduct weekly cardiotocography after fetal viability for FGR without AEDV or reversed end‑diastolic velocity (REDV); increase to twice‑weekly or more when AEDV or REDV appears. [22][21]
• Do not rely solely on cardiotocography or biophysical profile, as a normal fetal heart‑rate tracing does not exclude progression of growth restriction. 22

Additional Doppler Studies (Society for Maternal‑Fetal Medicine)

• Routine use of middle cerebral artery, ductus venosus, or uterine artery Doppler is not recommended for standard clinical management of FGR. 22

Timing of Delivery Based on Umbilical Artery Doppler Findings

• Normal Doppler: Plan delivery at 38–39 weeks when estimated fetal weight is between the 3rd and 10th percentile. 22
• Decreased Diastolic Flow (not absent): Deliver at 37 weeks if Doppler shows decreased diastolic flow or if severe FGR (EFW < 3rd percentile) is present. 22
• Absent End‑Diastolic Velocity (AEDV): Deliver at 33–34 weeks, as neonatal morbidity outweighs prematurity risks at this gestation. Increase Doppler to 2–3 times weekly and cardiotocography to at least twice weekly. 22
• Reversed End‑Diastolic Velocity (REDV): Deliver at 30–32 weeks; admit for hospitalization with cardiotocography 1–2 times daily due to high risk of fetal demise. 22

Pre‑Delivery Interventions

Antenatal Corticosteroids

• Administer betamethasone or dexamethasone when delivery is anticipated before 34 weeks (or between 34 0/7 and 36 6/7 weeks if delivery is likely within 7 days). This is a GRADE 1A recommendation with the highest level of evidence. 22

Magnesium Sulfate for Neuroprotection

• Provide intrapartum magnesium sulfate for fetal neuroprotection when delivery is expected before 32 weeks gestation. This is also a GRADE 1A recommendation supported by multiple randomized trials. 22

Mode of Delivery Considerations

• For FGR pregnancies complicated by AEDV or REDV, cesarean delivery should be strongly considered based on the overall clinical picture. 22

Diagnostic Workup

• Chromosomal microarray analysis is advised for unexplained isolated FGR diagnosed before 32 weeks gestation; chromosomal abnormalities account for roughly 20 % of FGR cases. 22

Umbilical Artery Doppler for Suspected Intrauterine Growth Restriction (IUGR)

Indications for Doppler Surveillance

• Umbilical artery Doppler reduces perinatal mortality by 29 % in pregnancies with suspected IUGR and should be started immediately after diagnosis. 23
• Initiate weekly umbilical artery Doppler when the estimated fetal weight falls below the 10th percentile for gestational age. 23
• In pregnancies complicated by preeclampsia with fetal concerns, perform Doppler at the time of preeclampsia diagnosis and continue serially from 26 weeks until delivery if IUGR is confirmed. 24

Situations Where Doppler Is Not Recommended

• Routine screening of low‑risk pregnancies provides no benefit and should be avoided. 25
• Using Doppler predictively before IUGR develops is not supported because of absent standardised technique, gestational‑age windows, and abnormal‑flow criteria. 25

Surveillance Protocols Based on Doppler Findings

Normal Umbilical Artery Doppler

• Continue weekly Doppler assessments. 23
• Add weekly cardiotocography (NST or biophysical profile) after fetal viability is reached. 23
• If the estimated fetal weight remains between the 3rd and 10th percentile, schedule delivery at 38–39 weeks gestation. 23

Decreased End‑Diastolic Flow (Elevated Resistance >95th percentile)

• Increase surveillance to weekly Doppler examinations. 23
• Intensify cardiotocography frequency as clinically indicated. 26
• Plan delivery at 37 weeks gestation. 23

Absent End‑Diastolic Flow (AEDV)

• Administer antenatal corticosteroids when gestation is <34 weeks. Level I evidence supports mortality benefit for the umbilical artery. 23
• Perform Doppler 2–3 times per week. 23
• Conduct cardiotocography twice weekly or more often; some guidelines recommend daily monitoring. [23][24]
• Schedule delivery at 33–34 weeks gestation. 23
• Give magnesium sulfate for neuroprotection if delivery is anticipated <32 weeks. 24

Reversed End‑Diastolic Flow (REDV)

• Hospitalise the patient immediately. 26
• Give antenatal corticosteroids when gestation is <34 weeks. 23
• Perform cardiotocography 1–2 times daily. 26
• Increase Doppler to 3 times per week. 26
• Ensure daily consultant involvement in care. 26
• Plan delivery at 30–32 weeks gestation. 23
• Administer magnesium sulfate for neuroprotection if delivery is expected <32 weeks. 24

Management of Preterm (<34 weeks) Fetuses with AEDV or REDV

• Admit to hospital (mandatory for REDV). 26
• Give betamethasone 12 mg IM, repeat after 24 hours. 23
• Observe closely for 48–72 hours after corticosteroid administration. 23
• Provide magnesium sulfate (4–6 g IV loading dose) if delivery is anticipated <32 weeks. 24
• Intensify fetal surveillance with daily to twice‑daily cardiotocography. [24][26]
• Perform serial Doppler 2–3 times weekly. 23

Management of Term (≥37 weeks) with Any Abnormal Doppler

• Proceed to delivery irrespective of Doppler severity. 27
• Abnormal umbilical artery Doppler at term is itself an indication for delivery. 27

Mode of Delivery Considerations

• Cesarean delivery should be strongly considered for fetuses with AEDV or REDV because of severe placental insufficiency and high risk of intrapartum compromise. 26

Vessel Selection for Doppler Assessment

• The umbilical artery is the only vessel with Level I evidence demonstrating a reduction in perinatal mortality for IUGR management. 23
• Middle cerebral artery can identify brain‑sparing but lacks randomized‑trial evidence; no specific interventions have proven outcome benefit. 27
• Ductus venosus absent or reversed A‑wave predicts stillbirth with 100 % sensitivity, yet routine use is not recommended. 27
• Uterine artery may aid in refining IUGR diagnosis but is not advised for routine surveillance. 24

Predictive Sequence of Doppler Abnormalities

• Doppler changes follow a predictable progression: increased umbilical artery resistance → absent end‑diastolic flow → reversed end‑diastolic flow → venous Doppler abnormalities → abnormal fetal heart‑rate patterns. 28