What are the effects / risks
• Increased risk of IUGR and
premature birth (with anaemia
present at beginning of
pregnancy)
• Possible problems associated
with being cared for by a
weak / tired mother
http://www.chp.edu/CHP/P02462
What causes intrauterine growth restriction (IUGR)?
Intrauterine growth restriction results when a problem or abnormality prevents cells and tissues from growing or causes cells to decrease in size. This may occur when the fetus does not receive the necessary nutrients and oxygen needed for growth and development of organs and tissues, or because of infection. Although some babies are small because of genetics (their parents are small), most IUGR is due to other causes. Some factors that may contribute to IUGR include the following:
- Maternal factors:
- high blood pressure
- chronic kidney disease
- advanced diabetes
- heart or respiratory disease
- malnutrition, anemia
- infection
- substance abuse (alcohol, drugs)
- cigarette smoking
- Factors involving the uterus and placenta:
- decreased blood flow in the uterus and placenta
- placental abruption (placenta detaches from the uterus)
- placenta previa (placenta attaches low in the uterus)
- infection in the tissues around the fetus
- Factors related to the developing baby (fetus):
- multiple gestation (twins, triplets, etc.)
- infection
- birth defects
- chromosomal abnormality
Etiology
Many different factors cause IUGR, but they may be divided into two large categories, based on etiology. These categories include fetoplacental factors and maternal factors. Within the categories of maternal and fetoplacental factors are many specific causes (Table 1).
TABLE 1
Conditions Associated with Intrauterine Growth Retardation
Conditions Associated with Intrauterine Growth Retardation
Medical |
Chronic hypertension |
Preeclampsia early in gestation |
Diabetes mellitus |
Systemic lupus erythematosus |
Chronic renal disease |
Inflammatory bowel disease |
Severe hypoxic lung disease |
Maternal |
Smoking |
Alcohol use |
Cocaine use |
Warfarin (Coumadin, Panwarfin) |
Phenytoin (Dilantin) |
Malnutrition |
Prior history of pregnancy with intratuterine growth retardation |
Residing at altitude above 5,000 feet |
Infectious |
Syphilis |
Cytomegalovirus |
Toxoplasmosis |
Rubella |
Hepatitis B |
HSV-1 or HSV-2 |
HIV-1 |
Congenital |
Trisomy 21 |
Trisomy 18 |
Trisomy 13 |
Turner's syndrome |
Historically, IUGR has been categorized as symmetric or asymmetric. Symmetric IUGR refers to fetuses with equally poor growth velocity of the head, the abdomen and the long bones. Asymmetric IUGR refers to infants whose head and long bones are spared compared with their abdomen and viscera. It is now believed that most IUGR is a continuum from asymmetry (early stages) to symmetry (late stages).
Maternal causes of IUGR account for most uteroplacental cases. Chronic hypertension is the most common cause of IUGR. Moreover, the infants of hypertensive mothers have a three-fold increase in perinatal mortality compared with infants with IUGR who are born of normotensive mothers. Because of their significant risk, one author6 recommends delivering these infants by 37 weeks of gestational age.
Preeclampsia causes placental damage that results in uteroplacental insufficiency. The pathogenic mechanism is thought to be a failure of trophoblastic invasion by maternal spiral arterioles by 20 to 22 weeks of gestation.1 This failure causes luminal narrowing and medial degeneration, leading to diminished blood flow to the developing infant. Consequently, these infants fail to grow normally.
Infectious causes of fetal growth delay account for about 10 percent of all cases of IUGR. These causes include the “TORCH” group: Toxoplasma gondii, rubella, cytomegalovirus and herpes simplex virus types 1 and 2. Other potential pathogens include hepatitis A and hepatitis B, parvovirus B19, human immunodeficiency virus (HIV) and Treponema pallidum (syphilis).
Maternal prepregnancy weight and weight gain during pregnancy are considered strong indicators of birth weight.7 During World War II, a population of women in Leningrad who underwent prolonged malnutrition delivered infants with an average birth weight of 400 to 600 g (14 to 21 oz) less than expected.5 In a later study of Guatemalan Indians,8 it was found that protein malnutrition occurring before 26 weeks of gestation resulted in IUGR. The current consensus is that a maternal weight gain of less than 10 kg (22 lb) by 40 weeks of gestation is clearly a risk factor for IUGR.3
Maternal smoking may be the cause of 30 to 40 percent of U.S. cases of IUGR. One study9 found a dose-dependent decrease in fetal weight with an increasing number of cigarettes smoked each day (a 7.4 g [0.26 oz] decrease for each cigarette smoked per day). Another study10 found that women who smoked 11 or more cigarettes daily had infants weighing 330 g (11.5 oz) less than predicted and measuring 1.2 cm shorter than control subjects.
Early use of alcohol by the pregnant mother may lead to fetal alcohol syndrome, while second- or third-trimester use may result in IUGR. As little as one to two drinks per day have been shown to result in a growth-delayed child.11 Not surprisingly, maternal cocaine use has been linked to IUGR, as well as to reduced head circumference. Other drugs associated with IUGR include steroids, warfarin (Coumadin, Panwarfin) and phenytoin (Dilantin).
Intrauterine growth retardation occurs 10 times more frequently in twin deliveries than in single gestations. The incidence of IUGR in twins is about 15 to 25 percent.5 Decreased birth weight is second only to respiratory distress syndrome as a cause of infant mortality in twins. Reasons for IUGR in twin pregnancies include poor placental implantation, placental crowding and twin-to-twin transfusion.
