In brief — the direct answer
While Fetal Growth Restriction (FGR) specifically describes a baby who is not reaching their growth potential, the cause is often found in the relationship between the mother's health and the placenta. If the mother has underlying vascular issues, the placenta may not be able to deliver enough oxygen and nutrients, causing the baby to grow more slowly to conserve energy. At the MFM Unit, we manage FGR by looking at the 'whole picture'—optimizing the mother's health to give the baby the best possible environment for growth.
What is Fetal Growth Restriction (Maternal Aspects)?
From a maternal perspective, FGR is most often a problem of 'placental insufficiency.' The placenta is the engine of the pregnancy. If the mother's uterine arteries—the vessels supplying blood to the uterus—are resistant or narrow, the placenta cannot function at 100%. This is frequently associated with maternal high blood pressure or conditions that affect blood clotting.
Who is at risk?
Maternal factors that increase the risk of FGR include:
- Chronic Hypertension: Pre-existing high blood pressure.
- Autoimmune Diseases: Such as Lupus or Antiphospholipid Syndrome (APS).
- Kidney Disease: Which affects blood flow and pressure.
- Lifestyle: Smoking or poor nutrition can restrict placental efficiency.
- Small Maternal Size: Some mothers are naturally small, and their babies may be 'Small for Gestational Age' (SGA) without being pathologically restricted.
How we diagnose it
We investigate the mother alongside the baby:
- Uterine Artery Dopplers: Using ultrasound to measure the resistance of blood flow from the mother to the placenta. High resistance early in pregnancy is a warning sign.
- Blood Pressure Screening: Monitoring for signs of pre-eclampsia, which occurs in up to 30-50% of serious FGR cases.
- Blood Tests: Screening for clotting disorders or infections that might be affecting growth.
What does management involve?
The focus is on maternal optimization to support the baby:
- Blood Pressure Control: Keeping the mother's BP in a safe range without reducing placental blood flow too much.
- Low-dose Aspirin: Prescribed early (before 16 weeks) for women at high risk to help the placenta develop more effectively.
- Nutrition and Rest: While bed rest is no longer strictly recommended, avoiding physical stress and maintaining a protein-rich diet supports maternal wellbeing.
- Smoking Cessation: Stopping smoking is the single most effective lifestyle change to improve fetal growth.
What are the outcomes?
The goal is to deliver a healthy baby at the best possible time:
- Stability: By managing maternal conditions, we aim to prevent the sudden development of severe pre-eclampsia, allowing the baby more time in the womb.
- Postpartum: After delivery, we examine the placenta in the lab to understand why it was not functioning well. This helps us plan for the mother's next pregnancy to reduce the risk of FGR returning.
When to see a subspecialist
If you are told your 'fundal height' (the measurement of your bump) is small, or if your ultrasound shows a small baby, you should be evaluated by a Maternal-Fetal Medicine (MFM) specialist.
Dr. Gareth Waring leads our growth restriction service. We provide the expert surveillance needed to monitor the delicate balance between maternal health and fetal growth, ensuring both you and your baby are protected.
Questions to ask your doctor
References & Clinical Guidelines
- ISUOG Practice Guidelines: diagnosis and management of small-for-gestational-age fetus and fetal growth restriction
- Fetal Growth Restriction (Consult Series No. 52)
- The Investigation and Management of the Small-for-Gestational-Age Fetus (Green-top Guideline No. 31)
- Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality (Practice Advisory)