Fetal Growth Restriction / Intrauterine Growth Restriction (IUGR)
Intrauterine growth restriction is a condition that occurs when an unborn child is not growing properly, resulting in a smaller size than is developmentally appropriate. IUGR can be caused by placental issues, underlying maternal health issues, small parents, or some combination of these factors. IUGR puts the baby at risk of developing a number of serious problems, including low oxygen levels, reduced immune system function, hypothermia, and motor and neurological disabilities. IUGR is usually diagnosed prenatally by ultrasound based on risk factors or physical exams. It is essential that medical professionals conduct ultrasounds and other tests to monitor cases of IUGR. Babies with IUGR are typically unable to tolerate labor and contractions and are delivered before term. IUGR has many associated risks, including hypoxic-ischemic encephalopathy (HIE), fetal acidosis, and fetal death. Because this is such a serious problem, failing to properly monitor and perform a timely delivery before 40 weeks gestation constitutes medical malpractice.
Intrauterine growth restriction (IUGR), also called fetal growth restriction, is a condition in which an unborn baby is growing more slowly than normal. IUGR is present when a fetus’ weight falls below the 10th percentile for the corresponding gestational age. There are many causes, but most often IUGR involves poor maternal nutrition or lack of adequate oxygen supply to the baby. Babies afflicted with IUGR are at risk for a number of serious problems, including hypoxic-ischemic encephalopathy, cerebral palsy, and neurological problems.
Types of Intrauterine Growth Restriction (IUGR)
There are 2 major categories of IUGR: symmetrical and asymmetrical.
Asymmetrical IUGR is the more common of the two. In asymmetrical IUGR, there is a restriction of weight followed by length. The head continues to grow at normal or near-normal rates. This is a protective mechanism that promotes brain development. This type of IUGR is most commonly caused by extrinsic factors (maternal or uteroplacental) that affect the baby at later gestational ages.
Symmetrical IUGR is less common and is more of a cause for concern. This type of IUGR usually begins early in gestation. Since most neurons are developed by the 18th week of gestation, the fetus with symmetrical IUGR is more likely to have permanent neurological problems.
Causes of Intrauterine Growth Restriction (IUGR)
Intrauterine Growth Restriction has many possible causes. A common cause is a problem with the placenta. The placenta is the sac-like tissue that joins the mother and fetus. It carries oxygen and nutrients to the baby and permits the release of waste products from the baby. Placental abnormalities that may result in the development of fetal IUGR include partial placental abruption, wherein the placenta partially separates from the uterus, and an abnormally small placenta.
In addition to problems related to the placenta, IUGR can also occur when there are health problems with the mother, such as:
- Advanced diabetes
- High blood pressure (preeclampsia), heart disease, or pulmonary disease
- Infections such as rubella, cytomegalovirus, toxoplasmosis, and syphilis
- Kidney disease
- Malnutrition or anemia
- Sickle cell anemia
- Smoking, drinking alcohol, or abusing drugs
- Poor weight gain during pregnancy
Other possible causes include chromosomal defects in the baby or multiple gestations (twins, triplets, or more).
Risk Factors for Intrauterine Growth Restriction (IUGR)
Pregnancies that have any of the following conditions are at a greater risk for developing IUGR:
- Mother weighs less than 100 pounds
- Poor nutrition during pregnancy
- Birth defects or chromosomal abnormalities
- Use of drugs, cigarettes, and/or alcohol
- Pregnancy-induced hypertension (PIH)
- Placental abnormalities
- Umbilical cord abnormalities
- Multiple pregnancies
- Gestational diabetes
- Low levels of amniotic fluid (oligohydramnios)
Detecting and Diagnosing Intrauterine Growth Restriction (IUGR)
Intrauterine growth restriction is usually diagnosed by a medical professional during a routine prenatal exam—ultrasonic examinations and fundal height measurements (the distance from the pubic bone to the top of the uterus) are two common diagnostic measures. Although obstetricians have used fundal height measurements to estimate fetal growth for decades, modern research shows that fundal height measurements often fail to accurately and reliably diagnose intrauterine growth restriction. The American College of Obstetricians and Gynecologists (ACOG) explain that “ultrasonography remains the best method for evaluating the growth-restricted fetus.” Particularly in cases in which risk factors for IUGR are present, medical professionals are expected to provide ultrasounds. According to Danforth’s Obstetrics and Gynecology (2008), “normal fundal height in a woman with risk factors for IUGR does not provide sufficient reassurance” and “these women should still be followed with screening sonograms for fetal growth.” Since small babies are at risk of developing such severe injuries and medical problems, medical professionals must carefully and accurately diagnose IUGR by assessing risk factors and conducting the proper diagnostic tests.
If IUGR is suspected based on risk factors, fundal height measurements, or other indications, medical professionals must perform subsequent procedures in order to confirm the diagnosis and assess the baby’s health. Furthermore, if risk factors for IUGR are present, one or more of these procedures—most often ultrasounds—are performed regularly for the duration of the pregnancy. Diagnostic procedures include:
- Ultrasound. The main test for checking a baby’s growth in the uterus, ultrasound involves using sound waves to create pictures of the baby. Ultrasound can be used to measure the baby’s head and abdomen. The doctor can compare those measurements to growth charts to estimate the baby’s weight. Ultrasound can also be used to determine how much amniotic fluid is in the uterus. A low amount of amniotic fluid (oligohydramnios) could indicate IUGR.
- Doppler flow. Doppler flow uses sound waves to measure the amount and speed of blood flow through the blood vessels. This test is sometimes used to check the flow of blood in the umbilical cord and vessels in the baby’s brain.
- Weight checks. The mother’s weight is checked at every prenatal visit. If a mother is not gaining weight, it could indicate a growth problem in her baby.
- Amniocentesis. This is a procedure in which a needle is inserted through the mother’s abdomen and into her uterus to withdraw a small amount of amniotic fluid for testing. Tests may detect infection or some chromosomal abnormalities that could lead to IUGR.
- Fetal monitoring. The physician will initiate a regular schedule of prenatal tests up through the time of delivery, in order to assess the baby’s heart rate, growth, and level of amniotic fluid. These tests typically include weekly nonstress tests, biophysical profiles, and serial ultrasounds.
Upon diagnosis of IUGR, the mother may be referred to maternal-fetal specialists. These are physicians with specialized training and expertise in the management of IUGR. They should very carefully monitor the baby’s health throughout the remainder of the pregnancy.
Because of the extreme risk associated with moderate to severe fetal IUGR, many physicians will deliver their patients prior to term via cesarean section.
Treatment based on gestational age includes the following:
- If gestational age is 34 weeks or greater, the physician may recommend labor induction for an early delivery.
- If gestational age is less than 34 weeks, the physician will continue monitoring until 34 weeks or beyond. Fetal well-being and the amount of amniotic fluid will be monitored during this time. If either of these becomes a concern, then immediate delivery may be recommended. When delivery is suggested prior to 34 weeks, the physician should perform an amniocentesis to help evaluate fetal lung maturity.
Dangers of IUGR
Due to a lack of oxygen and nutrients in babies affected by IUGR, there is a decrease in the baby’s stores of glycogen and lipids, and this often leads to hypoglycemia at birth. This is a condition in which the amount of blood glucose (sugar) in the blood is lower than normal.
Polycythemia (increased red blood cells in the blood) can also occur in babies with IUGR. A baby suffering from IUGR may have chronically lowered oxygen levels. The baby’s body responds by producing extra red blood cells. Hypoxic-ischemic encephalopathy may also occur if oxygen levels are diminished for an extended period of time.
Other risks to the baby include the following:
- Hyperviscosity (decreased blood flow due to an increased number of red blood cells) Hypothermia (inability to maintain normal body temperature due to reduced fat on the body)
- Thrombocytopenia (low blood platelet count caused by placental insufficiency related to IUGR)
- Leukopenia (an abnormal decrease in the number of white blood cells, often reducing immune system function)
- Hypocalcemia (abnormally low blood calcium level)
- Pulmonary hemorrhage (acute bleeding from the lung)
- Meconium aspiration
- Motor and neurological disabilities
- Cerebral palsy
- Long-term cardiac problems
Depending on the cause of IUGR, a baby may be small all over or look malnourished upon delivery. The baby may be thin and pale and have loose, dry skin. The umbilical cord is often thin and dull instead of thick and shiny.
Intrauterine Growth Restriction (IUGR) and Medical Malpractice
When risk factors for IUGR are present or when IUGR is confirmed during pregnancy, it is essential that the physician properly assess and monitor the growth of the baby. In certain instances, it may be necessary to plan to deliver the baby early. Failure to treat the underlying cause of the IUGR and to properly monitor and plan for the birth can result in serious and permanent injuries and constitutes medical malpractice.
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Video: Intrauterine Growth Restriction and Birth Injury
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- Carlo WA. Prematurity andintrauterine growth restriction. In: Kliegman RM,Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders;2011:chap 91.
- Figueras F, Gardosi J. Intrauterine growth restriction: newconcepts in antenatal surveillance, diagnosis, and management. Am J Obstet Gynecol. 2011;204(4):288-300.