Intrauterine Growth Restriction (IUGR) for MCCQE1 Preparation

Introduction

Intrauterine Growth Restriction (IUGR) is a critical topic for the MCCQE1 exam and an essential concept in Canadian obstetric practice. This comprehensive guide will help you prepare for the MCCQE1 by covering key aspects of IUGR, focusing on Canadian guidelines and practices.

Epidemiology in the Canadian Context

• Prevalence: Approximately 3-7% of all pregnancies in Canada
• Higher rates observed in Indigenous populations and socioeconomically disadvantaged areas
• Risk factors specific to Canadian population:
  • Maternal smoking (still prevalent in ~10% of Canadian pregnancies)
  • Substance abuse, particularly opioids (an increasing concern in Canada)
  • Maternal malnutrition (more common in remote northern communities)

Etiology and Risk Factors

Classification of IUGR

1. Symmetric IUGR

   • Proportional reduction in fetal head and body size
   • Often associated with early onset and genetic causes

2. Asymmetric IUGR

   • Disproportionate reduction in fetal body size compared to head
   • Usually associated with placental insufficiency and later onset

Diagnosis

Diagnostic Criteria (Canadian Guidelines)

• Estimated fetal weight <10th percentile for gestational age
• Abdominal circumference <10th percentile
• Abnormal umbilical artery Doppler (elevated S/D ratio, absent or reversed end-diastolic flow)

Management

Management of IUGR in Canada follows a multidisciplinary approach, involving obstetricians, maternal-fetal medicine specialists, and neonatologists.

1. Maternal Interventions

   • Smoking cessation counseling
   • Nutrition optimization
   • Treatment of underlying medical conditions

2. Fetal Surveillance

   • Regular ultrasound assessments (every 2-4 weeks)
   • Biophysical profile scoring
   • Non-stress testing

3. Timing of Delivery

   • Individualized based on severity of IUGR and gestational age
   • Generally, delivery is recommended:
     • At 38-39 weeks for isolated IUGR with normal Doppler studies
     • Earlier for severe IUGR or abnormal Doppler findings

4. Mode of Delivery

   • Vaginal delivery if no contraindications
   • Cesarean section for obstetric indications or severe fetal compromise

Complications and Prognosis

IUGR can lead to various short-term and long-term complications:

Canadian Guidelines for IUGR Management

The Society of Obstetricians and Gynaecologists of Canada (SOGC) provides specific guidelines for IUGR management:

1. Universal screening for IUGR at 18-22 weeks gestation
2. Additional screening at 32-34 weeks for high-risk pregnancies
3. Use of customized fetal growth charts that account for maternal characteristics
4. Integration of Doppler studies in the management of IUGR
5. Consideration of antenatal corticosteroids for IUGR fetuses <34 weeks gestation

Key Points to Remember for MCCQE1

• IUGR is defined as fetal growth <10th percentile for gestational age
• Asymmetric IUGR is more common and often due to placental insufficiency
• Diagnosis involves clinical assessment, ultrasound, and Doppler studies
• Management is individualized based on severity and gestational age
• SOGC guidelines recommend universal screening at 18-22 weeks
• Consider antenatal corticosteroids for IUGR fetuses <34 weeks
• Long-term complications include increased risk of adult-onset diseases

MCCQE1 Mnemonic: "GROWTH"

• G: Gestational age assessment crucial
• R: Risk factors (maternal, fetal, placental)
• O: Oligohydramnios often associated
• W: Weight estimate <10th percentile
• T: Timing of delivery is key decision
• H: Head sparing in asymmetric IUGR

Sample Question

A 28-year-old G2P1 woman presents for routine prenatal care at 32 weeks gestation. Her fundal height measures 28 cm. Ultrasound reveals an estimated fetal weight at the 5th percentile with normal amniotic fluid volume. Umbilical artery Doppler shows increased resistance but present end-diastolic flow. Which of the following is the most appropriate next step in management?

• A. Immediate delivery by cesarean section
• B. Initiation of daily non-stress tests
• C. Repeat ultrasound and Doppler studies in 2 weeks
• D. Administration of antenatal corticosteroids
• E. Amniocentesis for fetal karyotyping

Explanation

The correct answer is:

• C. Repeat ultrasound and Doppler studies in 2 weeks

This case presents a scenario of suspected IUGR at 32 weeks gestation. The fundal height is lagging, and the estimated fetal weight is below the 10th percentile, which meets the criteria for IUGR. However, the amniotic fluid volume is normal, and while the umbilical artery Doppler shows increased resistance, there is still present end-diastolic flow.

Let's review the options:

A. Immediate delivery is not indicated at this gestational age without signs of severe fetal compromise. B. Daily non-stress tests would be overly aggressive at this stage, given the reassuring Doppler findings. C. Repeating the ultrasound and Doppler studies in 2 weeks is the most appropriate next step. This allows for close monitoring of fetal growth and placental function without unnecessary intervention. D. Antenatal corticosteroids are not routinely recommended at 32 weeks unless delivery is anticipated within 7 days. E. Amniocentesis for karyotyping is not indicated as the first step in this case, especially at this late gestational age.

According to Canadian guidelines, the management of IUGR involves serial ultrasounds and Doppler studies to monitor fetal growth and well-being. The frequency of these assessments depends on the severity of IUGR and gestational age. In this case, with mild IUGR and reassuring Doppler findings at 32 weeks, repeating the assessment in 2 weeks strikes the right balance between vigilance and avoiding unnecessary interventions.

References

1. Lausman A, Kingdom J. Intrauterine Growth Restriction: Screening, Diagnosis, and Management. J Obstet Gynaecol Can. 2013;35(8):741-748.

2. Society of Obstetricians and Gynaecologists of Canada. Intrauterine Growth Restriction: Diagnosis and Management. SOGC Clinical Practice Guideline No. 295, August 2013.

3. Figueras F, Gratacós E. Update on the Diagnosis and Classification of Fetal Growth Restriction and Proposal of a Stage-Based Management Protocol. Fetal Diagn Ther. 2014;36(2):86-98.

4. Statistics Canada. Health Fact Sheets - Smoking, 2018. https://www150.statcan.gc.ca/n1/pub/82-625-x/2019001/article/00006-eng.htm (opens in a new tab)

5. Public Health Agency of Canada. Perinatal Health Indicators for Canada 2017. Ottawa: Public Health Agency of Canada, 2017.