Failure of the fetus to grow properly in the uterus so that it is smaller than expected throughout the pregnancy
- Most common under the age of 17 or over the age of 34
- Smoking, alcohol or drug abuse, and an inadequate diet during pregnancy are risk factors
- Genetics as a risk factor depends on the cause
Also sometimes known as intra-uterine growth restriction or IUGR, intra-uterine growth retardation affects about 1 in 20 babies and occurs when a fetus fails to put on sufficient weight during pregnancy. On average, a baby weighs just over 3 kg (7 lb) at full term. A baby who has intra-uterine growth retardation may weigh less than 2.5 kg (5
What are the causes?
Poor fetal growth is usually caused by lack of nourishment, which may be due to a disorder in the mother or a factor in her lifestyle. The condition may also be caused by a problem with the placenta or a fetal abnormality.
Maternal disorders that may affect the function of the placenta and lead to malnourishment of the fetus include pre-eclampsia (see Pre-eclampsia and eclampsia), in which high blood pressure and other symptoms develop during pregnancy, chronic high blood pressure (see Hypertension), or pre-existing kidney failure. Poor fetal growth can also be caused by a serious infection in the mother, such as rubella. In addition, several factors in the mother’s lifestyle are thought to be linked to intra-uterine growth retardation. Smoking, abusing alcohol or drugs, and eating an inadequate diet may all affect levels of nutrients passing across the placenta to nourish the fetus.
In addition, there are problems with the placenta itself that may lead to fetal malnourishment. For example, part of the placenta may separate from the wall of the uterus (see Placental abruption). Rarely, an inherited or a chromosomal abnormality in the fetus, such as Down’s syndrome, leads to intra-uterine growth retardation.
What might be done?
You will probably have no symptoms, but your doctor may be concerned if measurements of your abdomen during pregnancy show that your uterus is not increasing in size at the normal rate. You will have regular ultrasound scans to monitor the rate of growth of the fetus and may be given scans that measure blood flow through the umbilical cord to the fetus (see Ultrasound scanning in pregnancy).
If intra-uterine growth retardation is diagnosed, you may need to be admitted to hospital for observation. You will be treated for any underlying condition, if possible. For example, you may be given drugs to treat high blood pressure. If your diet is inadequate, you may be offered dietary advice. The fetus’s heartbeat will probably be monitored twice daily. If the fetus continues to grow slowly, it may be delivered early, either by induction of labour or by caesarean section.
What is the prognosis?
After they are born, small babies may initially need to be monitored and cared for in a special care baby unit because they tend to be more susceptible to problems such as infections, low blood glucose, and low body temperature (hypothermia). Most small babies gain weight rapidly and reach a normal size. Having a small baby slightly increases the risk of your next baby also being small. However, each new baby tends to be larger than the last.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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