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If that happens again, usually in a subsequent pregnancy, it will trigger a much bigger production of the antibodies. The antibodies will cross over, attack and destroy that baby’s Rhesus Positive cells.  With this relentless attack on the baby’s red blood cells, the baby becomes progressively anemic.

 

This is the main reason why any Rhesus negative mother should be protected against possible sensitization.

 

The baby's heart may also fail as a result of infection by some viruses which attack the myocardium (the heart muscle). This is a rare occurrence. There are various other rarer causes of fetal heart failure.

 

Excessive fetal urine production

If the fetus has inherited a condition known as diabetes insipidus, then the problem manifest itself as an increase in fluid volume.

Individuals with this condition have impairment in the regulatory mechanism in urine production. They end up producing excessive amounts of urine; in the case of the fetus, this overwhelms the fluid removal mechanism.

Another cause of excessive urine production by the fetus is in cases of identical twins that develop a complication of twin-to-twin transfusion (TTTS). This means that one twin's blood is transfused into the other's circulation. The recipient twin tries to cope by increasing its urine production.

 

This condition may cause a rapidly increasing maternal abdominal girth, which may cause extreme discomfort to the mother. It is a dangerous condition that might end up with the loss of one or both twins. This is discussed in greater detail in the section titled "Twins and multiple pregnancy".

 

Symptoms of excessive amniotic fluid

It may be difficult for the affected mother to suspect that she has excessive fluid. Most cases of increased amniotic fluid volume develop insidiously. A midwife or a doctor may be the first person to draw attention to the fact that the fluid may be increased, following a routine examination.

 

Occasionally, the uterine distension produced by the excess fluid may cause abdominal discomfort. This tends to creep in by stealth.

 

The only exception to this presentation is in twin-to-twin transfusion. Here, the development of excess fluid is rapid and therefore the discomfort appears quickly and can be quite marked and distressing to the mother.

 

Effect of polyhydramnios on pregnancy outcome

Effect of excessive amniotic fluid volume is usually directly dependent on the cause of the excess. There is no doubt that, taken overall as a group, excess fluid (polyhydramnios) has a less favorable outcome compared to where fluid volume is normal. However, this is a heterogeneous group covering a wide spectrum.

 

At one end there is the group with severe fetal abnormalities such as anencephaly (absent brain tissue). This condition is incompatible with life outside the womb. At the other end, there is excess fluid where the cause cannot be found. Almost all in the latter group have a good outcome.

 

In the middle, there are various causes whose result will depend on their nature, severity and how effective the management is.

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