Fetal growth restriction (FGR) affects roughly 5% to 10% of all pregnancies worldwide, making it one of the more common complications of pregnancy. The condition is defined as a baby whose estimated weight or abdominal circumference falls below the 10th percentile for their gestational age on ultrasound. That said, rates vary significantly depending on where you live, what health conditions are present, and how screening is done.
Why Rates Vary So Much
The 5% to 10% range is wide because FGR depends heavily on the population being studied. In high-income countries with good prenatal care and nutrition, rates tend to cluster closer to 5%. In low-income settings, where malnutrition, infection, and limited healthcare access are more common, the figure rises substantially. Multiple pregnancies (twins, triplets) also drive up the overall number, since carrying more than one baby increases the chance that at least one will be growth restricted.
Detection also plays a role. FGR is frequently missed when the only screening tool is a tape measure across the abdomen (fundal height measurement), which catches only about 43% of affected pregnancies. Standard ultrasound picks up roughly 86% of cases, and handheld portable ultrasound may detect even more. In places where ultrasound access is limited, many cases simply go undiagnosed, which means reported prevalence can undercount the true rate.
Who Is Most at Risk
The biggest driver of FGR is a problem with the placenta. In a healthy pregnancy, the placenta establishes a rich blood supply by remodeling the small arteries in the uterine wall. When that process is incomplete, blood flow to the placenta is reduced, and the baby doesn’t receive enough oxygen and nutrients to grow on track. This placental insufficiency is behind the majority of late-onset cases.
Several maternal health conditions raise the likelihood:
- Preeclampsia and high blood pressure: These directly reduce blood flow through the placenta.
- Diabetes: Both pre-existing and gestational diabetes can impair placental function.
- Kidney disease and clotting disorders: Both affect the vascular system that feeds the placenta.
- Smoking, alcohol, and drug use: Smoking alone is one of the most preventable risk factors for FGR.
- Poor nutrition or very low pre-pregnancy weight: The body needs adequate calories and micronutrients to sustain fetal growth.
- Thyroid disease and anemia: Both affect oxygen delivery and metabolism.
- Living at high altitude: Lower oxygen levels at elevation can limit fetal growth.
In a smaller percentage of cases, the cause is on the baby’s side. Chromosomal abnormalities and structural birth defects account for up to 20% of early-onset FGR (diagnosed before 32 weeks). Fetal infections, though less common, can also restrict growth.
Early-Onset vs. Late-Onset FGR
Not all growth restriction is the same. Early-onset FGR, typically identified before 32 weeks of pregnancy, tends to be more severe and is more likely to involve a genetic or structural problem. It is also associated with more significant effects on brain development, including widespread injury to the brain’s white matter and signs of inflammation in brain tissue. Because of this, guidelines recommend that when FGR appears before 32 weeks, genetic testing should be offered to look for chromosomal abnormalities.
Late-onset FGR, detected after 32 weeks, is more commonly caused by placental insufficiency that gradually worsens in the third trimester. While it tends to be milder, it still carries real risks and can affect brain development in different ways. Both forms require close monitoring, but early-onset FGR generally means more intensive surveillance and earlier delivery planning.
Recurrence in Future Pregnancies
If you’ve had one pregnancy affected by FGR, the chance of it happening again is roughly 20% to 30%. That’s considerably higher than the baseline rate, but it still means the majority of subsequent pregnancies will not be affected. Unfortunately, there are no proven medications that reliably prevent recurrence. Clinical guidelines specifically recommend against using blood thinners, sildenafil, or bed rest solely to prevent FGR from recurring, as none of these have shown benefit for this purpose.
What does help is early and thorough monitoring in the next pregnancy, including serial ultrasounds to track growth, along with managing any underlying conditions like high blood pressure or diabetes before conception.
Long-Term Health Effects for the Baby
The consequences of FGR don’t always end at birth. Babies born growth restricted face higher rates of complications in the newborn period, but research over the past two decades has revealed that the effects can extend well into adulthood. People who were growth restricted in the womb have a significantly higher incidence of cardiovascular disease, including high blood pressure, coronary artery disease, and heart failure later in life.
The link to metabolic problems is equally strong. FGR is associated with insulin resistance, which can lead to type 2 diabetes, fatty liver disease, and abnormal cholesterol levels. Chronic kidney disease and impaired lung function have also been documented. Young adults born after FGR show higher systolic blood pressure and stiffer arteries compared to peers who grew normally in the womb.
These long-term risks don’t mean every growth-restricted baby will develop chronic disease, but they do suggest that children born with FGR may benefit from cardiovascular and metabolic monitoring as they grow up. Some research points to nutritional strategies, including specific fatty acid supplementation in infancy, as a potential way to improve developmental outcomes, though this remains an active area of investigation.
How FGR Is Detected
At routine prenatal visits, your provider measures the distance from your pubic bone to the top of your uterus (fundal height) to get a rough sense of whether the baby is growing on track. This method is simple and cheap, but it misses more than half of growth-restricted babies. Its sensitivity is only about 43%, meaning it correctly flags fewer than half of the pregnancies where FGR is actually present.
Ultrasound is far more reliable. A standard ultrasound measuring the baby’s estimated weight and abdominal circumference detects about 86% of FGR cases. When growth restriction is suspected, your provider will typically order serial ultrasounds every two to four weeks to track the pattern. A single measurement below the 10th percentile can be concerning, but the trend over time is what confirms the diagnosis and guides decisions about timing of delivery.
Doppler ultrasound, which measures blood flow through the umbilical cord and other fetal vessels, adds another layer of information. It can reveal whether the placenta is delivering enough blood to the baby and help distinguish between a baby who is constitutionally small but healthy and one who is genuinely growth restricted due to poor placental function.