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)?
Placental dysfunction can limit oxygen and nutrient transfer, but FGR has more than one possible cause. Maternal hypertension, kidney or autoimmune disease may contribute. Uterine artery resistance is one marker and does not by itself diagnose a narrow or blocked artery. SGA describes size and includes both healthy small fetuses and fetuses with FGR.
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
Review maternal history, medications, blood pressure, urine and the fetal assessment together. Blood tests should answer a defined clinical question, such as suspected pre-eclampsia or antiphospholipid syndrome; broad inherited-thrombophilia or infection panels are not automatically indicated for every small fetus. The team considers anatomy, gestation and other findings when offering fetal genetic or infection testing.
What does management involve?
Treat maternal disease according to pregnancy guidance and support smoking cessation and appropriate nutrition. Routine bed rest is not a treatment for FGR. Aspirin may be prescribed for pre-eclampsia prevention in eligible pregnancies, but does not reverse established FGR and is not automatically indicated for an isolated prior small baby. Plan fetal surveillance and delivery alongside maternal assessment.
What are the outcomes?
Treatment supports maternal health and informs birth planning but cannot guarantee continued growth or prevent every case of pre-eclampsia. Placental examination and a postnatal review may clarify the cause and help plan a future pregnancy.
When to see a subspecialist
Seek specialist assessment for a small or slowing fetus, abnormal Doppler or maternal disease. Reduced movements and symptoms of pre-eclampsia require prompt maternity assessment. Bring previous pregnancy and placental reports if available.
Questions to ask your doctor
References & Clinical Guidelines
- Practice Guidelines: ultrasound assessment of fetal biometry and growth
- Practice Guidelines: diagnosis and management of SGA and fetal growth restriction
- Consult Series #52: Diagnosis and management of fetal growth restriction
- Green-top Guideline No. 31: investigation and care of a small fetus — includes July 2026 correction
- July 2026 growth-guideline update following NHS England’s INTERGROWTH decision
- Low-Dose Aspirin Use During Pregnancy: indications and evidence limits