Fetal Growth Restriction
Fetal growth restriction (FGR), formerly called intrauterine growth restriction (IUGR), is a condition in which an unborn baby (fetus) is smaller than expected for the number of weeks of pregnancy (gestational age).Newborn babies with FGR may be called “small for gestational age.”
Mild FGR usually doesn’t cause long-term problems. In fact, most babies who have it catch up in height and weight by age 2. But severe FGR can seriously harm a baby before and after birth. The extent of the problems depends on the cause and how severe the growth restriction is. It also depends on what point in the pregnancy it starts.
Classification –
Fetal growth restriction (FGR) is usually classified as symmetric and asymmetric.
• Symmetric growth restriction implies a fetus whose entire body is proportionally small.
• Asymmetric growth restriction implies a fetus who is undernourished and is directing most of its energy to maintaining growth of vital organs, such as the brain and heart, at the expense of the liver, muscle and fat. This type of growth restriction is usually the result of placental insufficiency.
A fetus with asymmetric IUGR has a normal head dimension but a small abdominal circumference (due to decreased liver size), scrawny limbs (because of decreased muscle mass) and thinned skin (because of decreased fat). If the insult causing asymmetric growth restriction is sustained long enough or is severe enough, the fetus may lose the ability to compensate and will become symmetrically growth-restricted. Arrested head growth is of great concern to the developmental potential of the fetus.
Symptoms –
The main symptom of FGR is a baby that is small for his or her gestational age. Specifically, the baby’s estimated weight is below the 10th percentile — or less than that of 90% of babies of the same gestational age.
Depending on the cause of FGR, the baby may be small all over or look malnourished. They may be thin and pale and have loose, dry skin. The umbilical cord is often thin and dull instead of thick and shiny.
Not all babies that are born small have FGR, though.
Causes –
Fetal growth restriction (FGR) has many possible causes. A common cause is a problem with the placenta. The placenta is the tissue that joins the mother and fetus, carrying oxygen and nutrients to the baby and permitting the release of waste products from the baby.
The condition can also occur as the result of certain health problems in the mother, such as:
• Infections such as rubella, cytomegalovirus, toxoplasmosis, and syphilis
• Advanced diabetes
• Autoimmune disease
• High blood pressure or heart disease
• Malnutrition or anemia
• Kidney disease or lung disease
• Sickle cell anemia
• Smoking, drinking alcohol, or abusing drugs
Factors in the baby that can cause FGR include:
• Being one of a twin or triplets
• Infections
• Birth defects, such as heart defects
• Problem with genes or chromosomes
• living at an altitude above 5,000 feet.
▪︎FGR and Twin Risks
Twins are usually smaller than usual. But FGR also affects up to 25% of twin pregnancies.
Twins who share a placenta may:
• Have an uneven share of blood and nutrients between them. As a result, one twin may be much smaller. This is called selective intrauterine growth restriction.
• Share blood vessels. They may develop a serious condition called twin-twin transfusion syndrome (TTTS). When this happens, there is an unequal exchange of blood between the twins, putting them both at risk.
• Share an amniotic sac. Then the umbilical cords may become tangled, cutting off blood flow to one or both twins.
Complications –
• Premature birth and low birth weight
• Low Apgar scores (a test given just after birth to check the newborn’s physical condition and whether it needs special medical care)
• Trouble handling the stresses of vaginal delivery
• Meconium aspiration (when the baby inhales its own stools passed while in the uterus), which can lead to breathing problems
• Decreased oxygen levels
• Unusually high red blood cell count
• Hypoglycemia (low blood sugar)
• Low resistance to infection
• Trouble controlling body temperature
In the most severe cases, FGR can lead to stillbirth. It can also cause long-term growth problems.
Diagnosis –
One of the main reasons for regular prenatal exams is to make sure your baby is growing well. During pregnancy, the size of your baby is estimated in different ways, including:
• Fundal height. To check fundal height, your healthcare provider measures from the top of your pubic bone to the top of your uterus (fundus). Fundal height, measured in centimeters (cm), is about the same as the number of weeks of pregnancy after the 20th week. For example, at 24 weeks gestation, your fundal height should be close to 24 cm. If the fundal height is less than expected, it may mean FGR.
If your healthcare provider thinks you have FGR, you will have other tests. These include:
• Fetal ultrasound. Estimating fetal weight with ultrasound is the best way to find FGR. Ultrasound uses sound waves to create images of the baby in the womb. Sound waves will not harm you or the baby. Your healthcare provider or a technician will use the images to measure the baby. A diagnosis of FGR is based on the difference between actual and expected measurements at a certain gestational age.
• Doppler ultrasound. You may also have this special type of ultrasound to diagnose FGR. Doppler ultrasound checks the blood flow to the placenta and through the umbilical cord to the baby. Decreased blood flow may mean your baby has FGR.
You may have repeat ultrasound exams, Doppler studies, and other tests.
Management –
Management depends on how serious the fetal growth restriction (FGR) is. This is based on the ultrasound (estimated fetal weight) and Doppler ultrasound (blood flow to the baby), as well is risk factors and the number of weeks gestation.
Treatment may include:
• Frequent monitoring.This means you will have prenatal visits more often, and ultrasound and Doppler ultrasound exams. You may have other tests.
• Tracking fetal movements. Your healthcare provider may also ask you to keep track of fetal movements. If so, he or she will give you instructions.
• Corticosteroid medicine
• Hospital stay
• Early delivery or emergency cesarean
Prevention –
Although fetal growth restriction (FGR) can occur even when a mother is perfectly healthy, there are things mothers can do to reduce the risk of FGR and increase the odds of a healthy pregnancy and baby.
• Keep all of your prenatal appointments. Detecting potential problems early allows you to treat them early.
• Eat healthfully. Healthy foods and ample calories help keep your baby well nourished.
• Be aware of your baby’s movements. A baby who doesn’t move often or who stops moving may have a problem. If you notice changes in your baby’s movement, call your doctor.
• Check your medications. Sometimes a medication a mother is taking for another health problem can lead to problems with her unborn baby.
• Get plenty of rest. Rest will help you feel better and it may even help your baby grow. Try to get 8 hours of sleep (or more) each night. An hour or two of rest in the afternoon is also good for you.
• Practice healthy lifestyle habits. If you drink alcohol, take drugs, or smoke, stop for the health of your baby.
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