The rate of growth and the size of a fetus are affected by many different factors including the size of the mother and her diet. In most cases, a fetus will grow at a heathy rate and there are no problems. However, about 5% of fetuses grow much more slowly than others and are found to be in the 10
th percentile for size at their stage of development. This is known as intrauterine growth restriction or retardation. Intrauterine growth restriction retardation causes serious health problems in some babies, including low birth weight, premature birth, and in some cases stillbirth.
In most cases, intrauterine growth restriction is caused by problems with the mother’s placenta or its ability to provide nutrients and oxygen to the fetus. If the fetus does not receive the normal amount of nutrients it will grow more slowly, resulting in intrauterine growth retardation and low birth weight. The other causes are genetic and natural.
Medical Intrauterine Growth Restriction Retardation Causes
Medical causes of IUGR are causes that medically affect the woman’s blood or the ability for her placenta to provide nutrients to the baby. Preeclampsia, chronic hypertension, and other types of high blood pressure affect the functioning of the placenta, may damage the placenta and its vascular system, and are linked to constricted blood vessels in the placenta that reduce flow of nutrients.
Diabetes, lupus, lung disease, and kidney disease may also cause intrauterine growth restriction. In addition, if a woman is suffering from anemia or other blood disorders, this can affect the ability of her blood to carry oxygen and nutrients to the placenta and cause the fetus to grow more slowly.
Maternal Intrauterine Growth Restriction Retardation Causes
In addition to medical causes, there are other behaviors and characteristics of the mother that can result in IUGR and eventually a low birth weight. Smoking, alcohol, and cocaine use have all been shown to increase the risk of IUGR. Some experts believe that smoking may be the cause of one third of all IUGR cases in the United States. If the mother does not use alcohol during the first trimester but starts using it afterwards, the baby may not have any developmental disorders but may grow more slowly.
Studies have shown specific prescription drugs such as warfarin and phenytoin can also cause slower growth of the fetus. If the mother is not eating enough and suffering from protein deficiency, malnutrition, or other similar conditions, her body will not have enough nutrients to provide to the developing fetus. Living at high altitudes may also increase the risk of IUGR. This is because the decreased oxygen at these altitudes results in less oxygenated maternal blood and less oxygen provided to the baby.
Infectious Intrauterine Growth Restriction Retardation Causes
Certain types of infections, especially sexually transmitted infections, can result in health problems for the developing fetus, including IUGR. Some infections that have been linked to lower growth of the fetus include rubella, syphilis, hepatitis, HIV, and cytomegalovirus.
Genetic Intrauterine Growth Restriction Retardation Causes
Though rare, some cases of intrauterine growth restriction are caused by genetic issues and developmental abnormalities. Scientists have identified some gene defects that increase the likelihood of IUGR including Trisomy 21, Trisomy 18, Trisomy 13, and Turner’s syndrome.
Natural Intrauterine Growth Restriction Retardation Causes
Even though it is alarming to find out that a fetus is growing more slowly than 90% of fetuses, it sometimes is not caused by any infection, medical reasons, or genetic reasons. In some cases, the fetus is just smaller than normal. Naturally small fetuses are more likely to develop in women who are also in the tenth percentile for body weight and size. When IUGR is caused by natural causes, it typically will cause fewer adverse health effects for the newborn.
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