Foetal growth restriction is a pregnancy complication where the unborn baby grows more slowly than expected or does not reach its full growth potential. Managing this condition requires careful monitoring throughout pregnancy and after birth, with treatment decisions tailored to each individual situation and the stage at which growth restriction is detected.

Understanding Growth Challenges During Pregnancy

When a baby in the womb measures smaller than expected for the number of weeks of pregnancy, doctors use the term foetal growth restriction, also known as FGR or intrauterine growth restriction (IUGR). This condition affects approximately one in every ten pregnancies worldwide. The term describes babies whose estimated weight falls below the 10th percentile for their gestational age, meaning they weigh less than nine out of ten babies at the same stage of development.^[1][2]

It is important to understand that not every small baby has foetal growth restriction. Some babies are naturally small because their parents are small, and these babies are perfectly healthy despite their size. The key difference is whether the baby is achieving its own genetic growth potential or if something is preventing normal growth. Foetal growth restriction indicates an underlying problem that stops the baby from growing as it should, rather than simply being constitutionally small.^[3][4]

The main goal when managing foetal growth restriction is to monitor the baby’s wellbeing closely throughout pregnancy and determine the safest timing for delivery. Healthcare providers must carefully balance the risks of the baby remaining in the womb against the risks of premature birth. This involves regular assessments, specialized testing, and making informed decisions based on each unique pregnancy situation.^[2][11]

Why Foetal Growth Restriction Occurs

The causes of foetal growth restriction can come from problems with the mother’s health, issues with the placenta or umbilical cord, or conditions affecting the baby itself. The most common cause is a problem with the placenta, the organ that supplies nutrients and oxygen to the growing baby. When the placenta does not attach properly to the uterus or when blood flow through the umbilical cord is limited, the baby may not receive enough nourishment to grow normally.^[1][4]

Several maternal health conditions increase the risk of foetal growth restriction. High blood pressure, whether present before pregnancy or developing during pregnancy, can affect blood flow to the placenta. Women with diabetes, heart disease, kidney disease, or autoimmune conditions such as lupus face higher risks. Chronic lung conditions and severe anaemia (too few red blood cells) can also contribute to growth restriction. Additionally, lifestyle factors play a significant role: smoking cigarettes, drinking alcohol, or using recreational drugs during pregnancy all substantially increase the risk.^[1][3][6]

Infections during pregnancy can affect foetal growth. These include cytomegalovirus (CMV), rubella (German measles), toxoplasmosis, and syphilis. Some medications, particularly certain anti-seizure treatments, may also contribute to growth restriction. Women who are significantly underweight or who have poor nutrition and inadequate weight gain during pregnancy are at increased risk.^[5][13]

Conditions affecting the baby directly can also cause growth restriction. These include genetic disorders or chromosomal abnormalities such as Down syndrome (trisomy 21), structural birth defects particularly those affecting the heart or digestive system, and infections that the baby acquires in the womb. When a woman is pregnant with twins, triplets, or more babies, the risk of growth restriction increases significantly. For twins, the likelihood of being born too small can be as high as one in five pregnancies, and for triplets, three in five.^[1][4][12]

How Doctors Identify Growth Restriction

Regular prenatal examinations are essential for detecting foetal growth restriction. One of the main purposes of these routine visits is to ensure that the baby is growing appropriately. Healthcare providers typically begin checking foetal growth by measuring the fundal height, which is the distance from the top of the pubic bone to the top of the uterus. This measurement, taken in centimetres, should roughly correspond to the number of weeks of pregnancy after the 20th week. For example, at 24 weeks of gestation, the fundal height should be approximately 24 centimetres. If this measurement is smaller than expected, it may indicate foetal growth restriction and prompt further investigation.^[1][4][6]

When growth restriction is suspected, the most reliable method for confirmation is ultrasound examination. During this test, high-frequency sound waves create images of the baby inside the uterus. The ultrasound technician or doctor measures specific parts of the baby, including the circumference of the head and abdomen, and the length of the thigh bone. These measurements, combined with the gestational age, allow doctors to estimate the baby’s weight and compare it to standard growth charts. A diagnosis of foetal growth restriction is typically made when the estimated foetal weight falls below the 10th percentile.^[1][5][6]

Ultrasound examinations can also identify other important information. They can reveal problems with the placenta, assess the amount of amniotic fluid surrounding the baby, and check blood flow through the umbilical cord and to the placenta using a technique called Doppler velocimetry. This specialized ultrasound measures how blood moves through vessels and can indicate whether the baby is receiving adequate oxygen and nutrients.^[2][13]

Additional tests may be recommended depending on the situation. If foetal growth restriction is detected early in pregnancy (before 32 weeks), doctors may perform a detailed ultrasound examination to look for structural abnormalities or birth defects, as up to 20% of early-onset cases are associated with foetal or chromosomal abnormalities. Testing for certain infections that could affect the baby, such as cytomegalovirus (CMV), may be offered through amniocentesis (testing fluid from around the baby). Genetic testing, including chromosomal microarray analysis, may be recommended particularly when growth restriction is severe, occurs early, or is accompanied by other abnormalities.^[11][13]

Standard Management Approaches

Currently, there is no direct treatment that can cure foetal growth restriction or make the baby grow faster while in the womb. Instead, management focuses on careful monitoring to track the baby’s wellbeing and determine the optimal timing for delivery. The approach varies depending on when growth restriction is detected, how severe it is, and whether there are additional complications.^[4][12]

Once foetal growth restriction is diagnosed, healthcare providers implement a surveillance programme that includes regular ultrasound examinations to track foetal growth and assess the amount of amniotic fluid. These growth scans are typically repeated every one to two weeks. Doppler ultrasound studies of the umbilical artery are performed to evaluate blood flow from the placenta to the baby. When blood flow patterns are normal, these assessments may be done every one to two weeks. However, if blood flow is decreased or shows concerning patterns, monitoring may increase to weekly or even multiple times per week.^[11]

Cardiotocography (CTG), also known as foetal heart rate monitoring, is used to assess the baby’s wellbeing after viability (typically after 24 weeks). This non-invasive test records the baby’s heart rate and can detect signs of distress. For babies with foetal growth restriction without severely abnormal blood flow patterns, weekly CTG testing is typically recommended. When growth restriction is severe or blood flow patterns are significantly abnormal, the frequency of monitoring increases to at least once or twice daily.^[11]

Managing any underlying maternal health conditions is an important part of care. For women with high blood pressure, diabetes, or other medical conditions, following the treatment plan to keep these conditions well-controlled can help support the baby’s growth and reduce complications. However, most cases of foetal growth restriction cannot be prevented even with optimal management of maternal conditions.^[4][12]

The timing of delivery is one of the most critical decisions in managing foetal growth restriction. This decision must balance the risks of prematurity against the risks of the baby remaining in the womb. Babies with growth restriction face increased risks of stillbirth if left in utero too long, but they also face complications from premature birth if delivered too early. The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine provide guidelines based on the severity of growth restriction, blood flow patterns, and gestational age. For babies with normal blood flow patterns and mild growth restriction, delivery may be planned around 37 weeks. However, when blood flow is severely abnormal or the baby shows signs of distress, earlier delivery may be necessary, sometimes requiring emergency caesarean section.^[7][11][14]

Some healthcare providers may recommend giving corticosteroid injections to the mother if early delivery is anticipated. These medications help mature the baby’s lungs more quickly, reducing breathing problems after birth. Hospitalization may be necessary for close monitoring, particularly when growth restriction is severe or blood flow patterns become concerning.^[11]

Prevention Strategies and Their Limitations

Despite extensive research, there are no evidence-based measures that have been proven to prevent foetal growth restriction directly. Numerous interventions have been studied, but most have shown limited or no benefit. Nutritional treatments and dietary supplements, including specific vitamin combinations, protein supplementation, and calorie-dense supplements, have been evaluated in multiple studies but have not been shown to prevent foetal growth restriction.^[14][19]

Blood-thinning medications such as heparin or low-molecular-weight heparin should not be prescribed solely for preventing foetal growth restriction, as clinical trials have not demonstrated effectiveness for this purpose. Similarly, there is no evidence supporting bed rest or reduced activity as preventive measures.^[11][14][19]

One intervention that may have an indirect benefit is low-dose aspirin. While aspirin is not prescribed specifically to prevent foetal growth restriction, it is recommended for women at moderate or high risk of developing preeclampsia (a serious pregnancy complication characterized by high blood pressure). This medication is typically started between 12 and 16 weeks of pregnancy. Because preeclampsia and foetal growth restriction share some common underlying mechanisms related to placental function, aspirin therapy for preeclampsia prevention may also reduce the likelihood of developing growth restriction in high-risk pregnancies.^[14][19]

The most effective approaches to supporting healthy foetal growth involve optimizing maternal health before and during pregnancy. This includes managing chronic medical conditions, maintaining a healthy weight, eating a balanced diet, avoiding tobacco smoke, alcohol, and recreational drugs, and attending all scheduled prenatal appointments for early detection and management of any problems that develop.^[4][12]

Care for Babies After Birth

Babies born with foetal growth restriction often require specialized care immediately after delivery and in the days and weeks that follow. Many of these babies are delivered at least a few weeks early, and some arrive via emergency caesarean section. A neonatology team may need to provide emergency care such as breathing support, heart rate monitoring, or resuscitation at birth.^[17]

Newborns affected by foetal growth restriction commonly experience several health issues in their first hours and days of life. Low blood sugar (hypoglycaemia) is one of the most frequent problems, typically appearing within the first 24 hours after delivery. These babies may need constant sugar intake through frequent feedings or intravenous fluids to maintain stable blood sugar levels. In most cases, blood sugar normalizes within four to five days, though it can persist longer in severe cases. Maintaining adequate blood sugar is critical because chronically low levels can damage brain tissue and affect lifelong learning and development.^[1][6][17]

Temperature regulation can be difficult for these small babies. They may have trouble maintaining normal body temperature and need to be kept in a warmed incubator. Low birth weight babies may also have difficulty fighting infections and may have higher levels of red blood cells (polycythaemia), which can cause complications. Breathing problems, particularly in premature babies, may require respiratory support. Some babies need specialized care in the neonatal intensive care unit (NICU) for days or weeks.^[1][4][6]

Feeding can present challenges for babies with foetal growth restriction. These infants often need more calories and nutrients than are present in breast milk alone to help them grow and maintain stable blood sugar levels. For mothers who wish to breastfeed exclusively, this can be frustrating. Healthcare providers may recommend pumping breast milk and fortifying it with additional calories and protein, then feeding it to the baby through a bottle. Some feeding plans allow for two or three breastfeeding opportunities per day with the remainder of feeds being fortified. As the baby grows stronger and more mature, fortified feeds can be gradually decreased until exclusive breastfeeding becomes possible.^[17]

Long-term follow-up is important for children who experienced foetal growth restriction. These children face increased risks of various health issues as they grow. In early childhood, they may experience abnormal growth patterns, either remaining small or experiencing rapid catch-up growth. Blood pressure monitoring is recommended starting before three years of age for children born small for gestational age or who required neonatal intensive care. As they age, these individuals face higher risks of cardiac disease, metabolic syndrome including type 2 diabetes, neurodevelopmental difficulties, and reproductive health issues. Regular health monitoring can help identify and manage these problems early.^[14][19]

Research into New Approaches

Although clinical trials specifically focused on treating foetal growth restriction are limited, ongoing research continues to explore various interventions. Much of the research effort has focused on understanding the underlying mechanisms that cause placental dysfunction and restricted foetal growth. This includes studying the molecular pathways involved in placental development and function, investigating markers that can predict which pregnancies will develop growth restriction, and exploring potential therapeutic targets.

Past clinical trials have investigated several potential treatments, though most have not proven effective. Sildenafil, a medication that dilates blood vessels and was hypothesized to improve blood flow to the placenta, was studied in clinical trials but has shown insufficient benefit and potential safety concerns. Current recommendations advise against using sildenafil for in-utero treatment of foetal growth restriction.^[11]

Research into better diagnostic tools continues, including studies on novel biomarkers that might identify growth restriction earlier or predict which babies face the highest risks. Advanced ultrasound techniques and additional Doppler assessments of various blood vessels (including the ductus venosus, middle cerebral artery, and uterine arteries) are being studied to determine if they can improve management decisions, though current evidence does not support their routine clinical use beyond umbilical artery Doppler assessment.^[11]

The field continues to recognize that improved understanding of placental biology and foetal-placental interactions will be essential for developing effective therapies. Research institutions worldwide are working to identify safe and effective treatments, but to date, no medications or interventions have been proven to reverse growth restriction once it develops. The focus remains on early detection, careful monitoring, optimal timing of delivery, and appropriate care for affected babies after birth.

Most common treatment methods

• Enhanced foetal surveillance
  • Regular ultrasound examinations performed every one to two weeks to monitor foetal growth and amniotic fluid volume
  • Doppler velocimetry of the umbilical artery to assess blood flow patterns between the placenta and baby
  • Cardiotocography (foetal heart rate monitoring) performed weekly for mild cases or multiple times daily for severe cases
  • Serial assessments to detect deterioration and guide delivery timing decisions
• Timing of delivery
  • Carefully planned delivery timing that balances risks of prematurity against risks of continuing pregnancy
  • Delivery around 37 weeks for babies with normal blood flow patterns and mild growth restriction
  • Earlier delivery, sometimes by emergency caesarean section, when blood flow is severely abnormal or the baby shows signs of distress
  • Consultation with maternal-foetal medicine specialists to determine optimal delivery timing
• Maternal condition management
  • Treating and controlling underlying maternal health conditions such as high blood pressure, diabetes, or kidney disease
  • Low-dose aspirin therapy for women at risk of preeclampsia, which may indirectly reduce foetal growth restriction risk
  • Lifestyle modifications including smoking cessation, avoiding alcohol and recreational drugs
• Specialized neonatal care
  • Neonatal intensive care unit (NICU) monitoring and support for babies requiring specialized attention after birth
  • Management of hypoglycaemia (low blood sugar) through frequent feedings or intravenous glucose
  • Temperature regulation support using warmed incubators
  • Respiratory support for babies with breathing difficulties
  • Fortified feedings with additional calories and nutrients to support growth and maintain stable blood sugar
• Corticosteroid therapy
  • Antenatal corticosteroid injections given to mothers when early delivery is anticipated
  • Helps accelerate foetal lung maturity and reduce breathing problems after premature birth