What is Intrauterine Growth Restriction (IUGR)?
Did you ever wonder why a prenatal checkup with the obstetrician or midwife includes a measurement of the belly? It’s to check the growing baby’s size and identify if intrauterine growth restriction, or IUGR, is a concern. While it only occurs in 3 to 7 percent of all births, it tends to be more common with multiples and can be indicative of other health issues.
What is IUGR?
Intrauterine growth restriction, sometimes referred to as fetal growth restriction or small for gestational age (SGA), is a condition in which an unborn baby is not growing at a normal rate in the womb – the result is that the fetus is smaller than it should be for the gestational age.
There are two types of IUGR; primary, or symmetric, IUGR means that all of the baby’s organs are growing too small. Asymmetric, or secondary, IUGR means the head and brain develop normally but the abdomen is too small. Asymmetric is more common than symmetric IUGR.
It is also characterized as a fetal weight less than the 10th percentile, meaning it weighs less than 90 percent of all other fetuses at the same gestational age. Simple measurements, using the distance from the fundus, or top of the uterus, to the pubic bone, give a fairly accurate estimate of a baby’s size and can indicate growth issues. An ultrasound may then be performed to get more accurate measurements. If IUGR is found early or is particularly severe, amniocentesis testing will likely be recommended to determine if there is any other associated chromosomal issue. Regardless, the delayed growth can result in a host of complications during the pregnancy, delivery, and after the child is born.
IUGR risks include:
- Stress during a vaginal delivery
- Low Apgar scores, which is a test given just after birth to evaluate the baby’s condition
- Low birth weight
- Decreased oxygen levels
- Hypoglycemia, or low blood sugar
- Low resistance to infection
- Abnormally high red blood cell count
- Difficulty maintaining body temperature
- Long term growth problems
- Cerebral palsy
Newborns with IUGR may be thin and pale with dry skin; even their umbilical cord may appear thin and dull instead of thick and shiny. Not all babies will appear malnourished, but they will be small all over.
What causes IUGR during pregnancy?
It results when an abnormality prevents cells and tissues from growing properly, or it may cause cells to decrease in size. It can happen when a fetus is not receiving necessary nutrients required to develop properly, or because of an infection.
It can be related to health problems the mother is dealing with, including:
- Advanced diabetes
- High blood pressure or heart disease
- Infections like rubella, cytomegalovirus, toxoplasmosis, or syphilis
- Kidney or lung disease
- Malnutrition or anemia
- Sickle cell anemia
- Using cigarettes, alcohol or drugs during pregnancy
It’s also more common amongst women who conceive within 18 months of a previous birth. Factors specifically related to the uterus and placenta include:
- Decreased blood flow in the uterus and placenta
- Placental abruption, when the placenta detaches from the uterus
- Placenta previa, when the placenta attaches low in the uterus
- Infection in the tissues around the uterus
Factors related to the developing baby include:
- Multiples like twins or triplets
- Chromosomal abnormality or birth defects
Does IUGR affect brain development?
A 2015 study showed that infants with IUGR were at high risk for antenatal, perinatal and postnatal complications. Infants with moderate to severe IUGR “are at increased risk of stillbirth and likely to be born preterm… growth-restricted infants present a high-risk subgroup of infants with a complex and distinct set of microstructural brain abnormalities not observed in appropriately grown infants.”
Indeed, while babies with IUGR do not automatically experience long term brain damage or development issues, it does increase the risk for cerebral palsy. Cerebral palsy is a congenital disorder of movement, muscle tone or posture that can vary widely in severity. It is often marked by exaggerated reflexes, floppy or rigid limbs, and involuntary motion. Research indicates that the lower a baby’s size or weight due to IUGR, that more likely it is to have a more severe form of cerebral palsy. It’s unknown whether the slow growth causes brain damage, or if the damage occurs and results in IUGR. What we do know is that the postnatal period is critical; a baby’s brain grows by one percent each day in the few weeks after birth.
Can IUGR be treated?
Currently, there are no specific treatments for IUGR while the baby is in utero. The mother may be administered medications if she is dealing with any health issues, but it ultimately depends on the baby’s gestational age. If the baby is past 34 weeks, doctors may opt to deliver prematurely. If the condition is discovered before 34 weeks, they will likely monitor the situation closely until 34 weeks. At that point, they will decide if the baby has a better shot at getting stronger outside of the uterus rather than in. Multiples, which often deliver preterm anyway, may especially benefit if IUGR is preventing normal growth.
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