What are the RCOG (Royal College of Obstetricians and Gynaecologists) guidelines for fetal management in pregnant women?

RCOG Guidelines for Fetal Management

Definition and Diagnosis of Fetal Growth Restriction

The Royal College of Obstetricians and Gynaecologists (RCOG) defines fetal growth restriction (FGR) as either an estimated fetal weight (EFW) below the 10th percentile OR an abdominal circumference (AC) below the 10th percentile, which provides superior detection of small-for-gestational-age neonates compared to using EFW alone. 1, 2

• RCOG recommends using customized growth charts rather than population-based references to account for maternal characteristics that influence birthweight 1
• Severe FGR is defined as EFW less than the 3rd percentile, which significantly increases the risk of adverse perinatal outcomes 1
• The RCOG approach correctly identifies one additional case of SGA for every 14 patients assessed compared to methods using EFW alone 2

Initial Assessment and Screening

Risk Selection and Prevention

• All pregnant women should have fundal height measured at every antenatal visit from 24 weeks using customized growth charts 1
• Low-dose aspirin should be prescribed for women with major risk factors for placental insufficiency to prevent FGR 1, 3
• Smoking cessation counseling must be provided as smoking is a modifiable risk factor for FGR 1

Diagnostic Workup for Early-Onset FGR (<32 weeks)

• A detailed anatomical ultrasound examination is mandatory when FGR is diagnosed before 32 weeks, as up to 20% of cases are associated with fetal or chromosomal abnormalities 3, 4
• Chromosomal microarray analysis (CMA) should be offered for unexplained isolated FGR diagnosed before 32 weeks 3
• If fetal malformation or polyhydramnios accompanies FGR, CMA should be offered regardless of gestational age 3
• PCR testing for cytomegalovirus (CMV) is recommended when amniocentesis is performed for unexplained FGR 3

Surveillance Protocol

Initial Ultrasound Assessment

At the first diagnosis of FGR, perform comprehensive fetal biometry (biparietal diameter, head circumference, abdominal circumference, femur length), amniotic fluid volume assessment, and umbilical artery (UA) Doppler waveform analysis. 1

Serial Monitoring Schedule

• In confirmed FGR, serial evaluation of fetal growth, amniotic fluid volume, and UA Doppler should be performed from 24-26 weeks gestation until delivery 1
• Fetal biometry should be repeated no more frequently than every 2 weeks, as more frequent measurements do not improve outcomes and may lead to unnecessary interventions 1
• Seek maternal-fetal medicine specialist consultation for cases diagnosed before 24 weeks 1

Doppler-Based Surveillance Intensity

The frequency and intensity of monitoring is determined by UA Doppler findings:

• Normal UA Doppler: Continue 2-weekly growth scans with UA Doppler assessment 1
• Increased UA resistance (pulsatility index >95th percentile): Increase to weekly ultrasound surveillance 1
• Absent end-diastolic flow (AEDV) before 34 weeks: Daily cardiotocography (CTG), twice-weekly UA Doppler, and amniotic fluid assessment; discuss daily with consultant team 1, 3
• Reversed end-diastolic flow (REDV) before 30 weeks: Hospital admission with daily CTG, three times weekly UA Doppler and amniotic fluid assessment; obtain fetal medicine specialist opinion 1, 3

Cardiotocography Monitoring

• Weekly CTG testing after viability is recommended for FGR without AEDV/REDV 3
• Increase CTG frequency to at least 1-2 times daily when AEDV or REDV is present 3

Antenatal Interventions

Corticosteroids for Fetal Lung Maturation

Prenatal corticosteroids should be administered between 24+0 and 34+0 weeks gestation when preterm delivery is anticipated; RCOG uniquely recommends corticosteroids may be given up to 35+6 weeks, and even up to 38+0 weeks for elective cesarean delivery. 1

• Multiple courses of corticosteroids are not recommended 1

Magnesium Sulfate for Neuroprotection

• Magnesium sulfate for fetal neuroprotection should be administered before 32 weeks gestation when delivery is imminent 1, 3

Timing of Delivery

RCOG-endorsed delivery timing is based on the severity of FGR and UA Doppler findings:

Late-Onset FGR (≥32 weeks)

• EFW 3rd-10th percentile with normal UA Doppler: Delivery at 38-39 weeks 1, 3, 4
• EFW <3rd percentile OR decreased diastolic flow (without AEDV/REDV): Delivery at 37 weeks 1, 3, 4
• Absent end-diastolic velocity (AEDV): Delivery at 37-38 weeks (RCOG consensus with international guidelines) 1, 3

Early-Onset FGR (<32 weeks)

• AEDV: Delivery at 33-34 weeks 3, 4
• REDV: Delivery at 30-32 weeks 3, 4

A critical caveat: The single most important prognostic factor in preterm FGR is gestational age at delivery, with a 1-2% increase in intact survival for every additional day in utero up to 32 weeks, emphasizing the importance of balancing risks of prematurity against risks of ongoing placental insufficiency. 3

Mode of Delivery

• Cesarean delivery should be strongly considered for FGR complicated by AEDV or REDV based on the entire clinical scenario 3, 4
• Continuous electronic fetal monitoring during labor is mandatory for all cases of FGR, as these fetuses are at high risk for intrapartum hypoxia 1, 3
• Birthing pools should be avoided in FGR cases 1

Special Considerations

Hypertensive Disorders

• Maternal hypertensive disease is present in 50-70% of early-onset FGR cases and is associated with poorer outcomes including earlier delivery and lower birthweights 3, 4
• Close monitoring for development of preeclampsia is essential throughout pregnancy 3

Amniotic Fluid Assessment

• RCOG notes that amniotic fluid assessment has minimal value in diagnosing growth restriction but remains important for ongoing surveillance 1
• This contrasts with ACOG, which considers amniotic fluid an important diagnostic parameter 1

Common Pitfalls to Avoid

• Do not perform fetal biometry more frequently than every 2 weeks, as this leads to false-positive diagnoses of growth deceleration due to measurement error 1
• Do not delay delivery beyond recommended gestational ages based on Doppler findings, as stillbirth risk increases significantly in SGA fetuses from 38 weeks onward 1
• Always obtain specialist maternal-fetal medicine input for AEDV or REDV cases, as these require complex decision-making regarding delivery timing 1