Placental Insufficiency
Placenta doesn't deliver enough oxygen or food to the growing baby.

Placental Insufficiency During Pregnancy

Contents

• What Is Placental Insufficiency?
• What Causes It?
• What Are The Symptoms?
• How Is It Diagnosed?
• How Is It Treated?

Also called placental dysfunction, it is a complication of pregnancy whereby the placenta cannot deliver enough oxygen and nutrients to the growing baby. During pregnancy the fetus depends on the placenta and the umbilical veins for receiving oxygen and nutrients from the mother's blood, and for taking away carbon dioxide and other waste products. Because of the constancy of the mother's internal environment the composition of the blood reaching the placenta is unlikely to vary much except in rare conditions of maternal circulatory failure or asphyxia, or in cases of gross metabolic disturbance such as severe untreated diabetes or kidney disease. Even if the mother's diet is poor her blood will show little alteration, and this explains why a normal sized child may still be born to a mother with a bad diet. Fetal ill-health therefore seldom arises because of the quality of the mother's blood. If a problem arises, it is more likely to be due to a physical problem with the placenta itself.

What Causes It?

Restriction of the mother's blood flow through the placenta is the most common cause of placental insufficiency. Any restriction can have a serious effect upon fetal growth and development. Placental damage can cause restriction - damage for example caused by infarction (tissue death) or the separation from the uterine wall (placenta abruption). Spasm or blood clots in the placenta veins also have the same effect. In a few patients who give birth to babies who have obviously suffered from chronic placental insufficiency the placenta is small for no apparent reason. If pregnancy progresses beyond the due date (known as postmaturity) the placenta sometimes becomes inadequate for the needs of the large, still growing fetus. Although intrauterine fetal death before the onset of labor is rare, fetal distress may occur during labor. Intrauterine death may occur in cases of diabetes but the cause of this is uncertain. The fetus is often very large, but so is the placenta, and placental failure is not an adequate explanation. In cases of hemolytic disease (where the mother and fetus' blood groups are not compatible) the placenta is large but the fetus probably dies from cardiac failure caused by the severe hemolytic anemia rather than from placental insufficiency.

What Are The Symptoms?

Placental insufficiency usually does not produce any obvious symptoms, although there are certain clinical warning signs, namely inadequate:

1. Weight gain by the mother.
2. Growth of the uterus.
3. Growth of the fetus.
4. Fetal activity.

Doctors still don't fully under how the placenta works. Yet there is a need for doctors to identify those fetus at risk of intrauterine death due to placental insufficiency so that they can be delivered before this occurs.

Mothers weight
This should normally increase by about 1 pound a week after the first trimester, provided that the patient is not vomiting severely (hyperemesis gravidarum) and has no other disorder causing malnutrition. The components of this weight gain include the fetus, placenta, liquids, uterus, breasts and the fat store. In addition there is the increase in blood volume. These very diverse components are all dependent directly on placental function, or indirectly on it by way of the hormones it produces. Thus failure to gain weight adequately should be regarded as cause to carry out some placental function tests.

Uterine (womb) growth
This is not always easy to assess. To get technical - simple measurements of the height of the fundus above the pubis is more accurate than the common practice of assessing fundal height in relation to the umbilicus or xiphisternum. The fundal height should increase by about 1 cm weekly from the 16th week of pregnancy, and with an average sized fetus should equal the number of weeks of gestation plus or minus 2 cm. Measurements of abdominal girth are much less satisfactory indicators of uterine growth. If the uterus seems to be growing slowly this is another reason to perform placental function tests.

Fetal growth
The most reliable measurement of fetus growth are obtained with ultrasound. The best way to detect early signs of poor growth is to measure the abdominal circumference of the baby at the level of his liver and compare it to the size of his head. This technique calls for more sophisticated test and expertise on the part of the operator.

Fetal activity
The most important indicator of placental function is the well-being of the fetus. A valuable sign of a healthy fetus is vigorous activity. The mother may be able to give some indication of this by keeping a 'kick count'. She can be asked to note how frequently the baby moves in a given period, perhaps 30 minutes. Alternatively she can be asked to note how long it takes for the baby to move ten times.

A more sophisticated way of assessing fetal activity is to produce a continuous record of the fetal heart rate over a period of 30 minutes or more. This is done with a cardiotocograph and is often called a non-stress test. A change in rate with fetal activity and variability of the rate from beat to beat are associated with fetal health. The heart rate may change with a uterine contraction but the normal rate is restored as soon as the contraction passes off.

How Is It Diagnosed?

The mother's weight is taken at each prenatal visit, a below-average weight gain will be the first indication of a problem. Measuring the fundus height and observation of the baby during an ultrasound will give additional information. If it is suspected that the placenta is damaged further tests will be ordered.

The excretion of estrogen hormones (particularly estriol) in the mother's urine during a 24-hour period gives a consistent indication of placental health. Several urine tests will need to be repeated to observe trends (one test is not sufficient).

A still more elaborate method of fetal assessment is the biophysical profile. This is a score based on real-time ultrasound observations of fetal breathing and body movements, tone, quantity of amniotic fluid, and on a non-stress test. Lack of movements and amniotic fluid suggest the fetus is in danger of hypoxia (oxygen deprivation), but inactivity in the fetus may also be down to other non-dangerous reasons. Prolonged observation over more than 30 minutes may be necessary and even then there is a high false-positive rate. This test has therefore not been widely adopted in the U.S.

How Is It Treated?

Treating the underlying condition, if it is diabetes, kidney disease or high blood pressure during pregnancy is important. You may be confined to bed for the rest of your pregnancy. If a serious problem is detected and the fetus is viable (able to live outside the womb), labor induction may be recommended.

Expectations

If the baby does not receive enough oxygen and nutrients, this can affect its growth. In some cases it leads to a very low weight in the baby, a condition called intrauterine growth restriction (IUGR). IUGR increases the risk of pregnancy and delivery complications.

For more related complications, see the following:

• Kidney infection during pregnancy: Signs, diagnosis and treatment.
• Oligohydramnios: Too little amniotic fluid in the placenta.

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