Polyhydramnios - Symptoms & Treatment

The normal amount of amniotic fluid at term is approximately 1 litre. If the amount is thought to exceed 2 litres, then a condition of polyhydramnios is present. This is a potentially dangerous condition and occurs in about 3 per cent of all pregnancies.

Acute Polyhydramnios Information

Acute polyhydramnios is rare and invariably starts at the 24th week of pregnancy. There is a sudden, rapid enlargement of the uterus so that the abdominal girth may increase by as much as 15 or even 30 cm in a few days. This is associated with a twin pregnancy and nearly always with a uniovular (identical) twin pregnancy. Rapid enlargement of the uterus may result in considerable abdominal discomfort or even pain. Should this happen, the doctor must be notified.

The rapid uterine enlargement resulting from such a twin pregnancy usually continues for 7-10 days and then ceases.The pain and discomfort may be so severe that the woman has to be admitted to hospital for rest and special treatment. Premature labour may begin but the pregnancy usually continues satisfactorily and the twins, whose presence has been confirmed by ultrasonic scan, are delivered quite normally at the approprite time.

Chronic Polyhydramnios Information

Chronic polyhydramnios is usually first noted at about the 30th week of pregnancy, when the uterus enlarges to a degree greater than is expected.This is caused by the grossly increased amount of fluid within the uterus. The normal girth of a pregnant woman at term is approximately 100 cm but when polyhydramnios occurs the girth at 34 weeks may reach 100 cm, and at term may reach as much as 115 or 120 cm.

Chronic polyhydramnios results in a slow enlargement of the uterus and is not associated with pain or discomfort until the uterus becomes so large that its size creates discomfort.

The causes of chronic polyhydramnios are:

• Twin pregnancy.
• Diabetes.
• Pre-eclampsia.
• Congenital abnormality of the fetus.

Pregnancy and Polyhydramnios

More than 50 per cent of women suffering from polyhydramnios have no specific cause for the excessiveamount of fluid present. The large quantity of fluid over-distends the Uterus and predisposes the woman to premature labour which is best avoided by rest and following the doctor's advice meticulously. If the baby is in a large amount of amniotic fluid, it may not assume its correct position so that delivery should be in hospital where any abnormality of the baby's position can be corrected.Women with polyhydramnios are treated with special care during labour. The contractions of the over-distended uterus are relatively inefficient so that labour may be prolonged and assisted forceps delivery may be necessary during the second stage of labour. Weak uterine contractions during the third stage of labour may predispose the woman to bleeding after delivery, and she is usually given an injection of Syntocinon at the time of delivery as well as afterwards in order to prevent postpartum haemorrhage.

Polyhydramnios during pregnancy does not have a harmful effect on the development of the baby or on the woman after delivery, and there is no evidence to suggest that it will recur in a subsequent pregnancy.

Twin pregnancy and Polyhydramnios

Acute polyhydramnios starts at 24 weeks in a twin pregnancy and chronic polyhydramnios usually develops at about the 28th or 30th week in a gradual manner. The problems of twin pregnancy are discussed in Chapter 30. In actual fact twin pregnancies do not really suffer from polyhydramnios since there are two normal fetuses each with a normal amount of liquor, but the total amount of amniotic fluid is greater than normal and symptoms are exactly the same 'as for an excessive amount of fluid in a single pregnancy.

Diabetes and Polyhydramnios

Diabetic women who are carefully and rigidly controlled throughout their pregnancy have only a slightly increased incidence of polyhydramnios. If diabetes is uncontrolled or poorly controlled in pregnancy, there is a much higher incidence of polyhydramnios and the excessive amount of amniotic fluid is a direct result of the unstable diabetes.

Pre-eclampsia and Polyhydramnios

Some women with polyhydramnios develop pre-eclampsia. The reason for this is not known, but it may be there there is an association between the over-distended uterus and the blood supply to the kidney.

Congenital abnormality and Polyhydramnios

Polyhydramnios is one of the most important signs of some varieties of serious congenital abnormality. Up to 40 per cent of all single pregnancies which develop polyhydramnios do in fact harbour a baby suffering from a major degree of congenital abnormality.

Polyhydramnios caused by congenital abnormality usually begins at about the 30th week and is indistinguishable from polyhydramnios resulting from other causes. Abnormalities of the central nervous system and of the spine of the baby may make its swallowing mechanism ineffective, so that excess liquor accumulates within the amniotic sac. Abnormalities of the gullet, oesophagus or stomach may also result in defects of the swallowing mechanism and result in the formation of polyhydramnios.

Hopefully, all such severe abnormaliies of the fetus will have been detected by a detailed abnormality scan at 18-20 weeks' gestation. The problem will have already been addressed and so, these days, polyhydramnios in late pregnancy due to congenital abnormality should be a comparatively uncommon situation.