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There are other conditions that affect the muscles where the fetus is unable to effectively perform any activity requiring the use of muscles, including the act of swallowing. An infection by a virus called Coxsackie B which causes temporary paralysis is one example. It usually clears up in a couple of weeks. In the meantime, the mother will not feel any fetal movements at all.
What could cause the heart of the unborn baby to fail?
The heart is made up of muscle and, to function properly, it requires oxygen. If the amount of oxygen supplied to the heart muscle is insufficient, the heart will gradually fail. This can happen if the fetus is severely anaemic. Such severe anaemia may be caused by a condition destroying the baby's blood-cells.
This may happen in a mother with a Rhesus negative blood group if she becomes sensitised. If blood cells from a Rhesus positive baby find their way into the mother's circulation for the first time, they will trigger the production of antibodies against them. If that happens again, usually in a subsequent pregnancy, it will trigger a much bigger production of the antibodies, which cross over, attack and destroy that baby’s Rhesus positive cells. This is the main reason why any Rhesus negative mother should be protected against possible sensitisation.
The baby's heart may also fail as a result of infection by some viruses which home in to the heart muscles. This is a rare occurrence. There are various other causes of fetal heart failure which your doctor may wish to discuss with you. They are, however, uncommon.
What makes the fetus produce excessive amounts of urine?
If the fetus has inherited a condition known as diabetes insipidus, then the problem may appear as an increase in fluid volume. Individuals who have this condition have an 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.
A relatively commoner cause of excessive urine production by the fetus is in cases of identical twins who develop a complication of twin-to-twin transfusion. 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 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 further in Chapter 25, "Twins and multiple pregnancy").
What makes a pregnant woman suspect that she has developed increased fluid volume?
It is difficult. 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, during a routine examination. Occasionally, the uterine distension produced by the excess fluid may cause abdominal discomfort.
This creeps 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.
How does excess fluid affect the outcome of the pregnancy?
It depends on the cause of the excess. There is no doubt that, taken overall as a group, excess fluid (polyhydramnios) has a less favourable 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 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 of the latter have a good outcome.
In the middle, there are various causes whose result will depend on their nature and how severe it is. It is worth mentioning here that the result of excess fluid associated with gestational diabetes depends on how well-controlled the diabetes is.
Poorly controlled diabetes in pregnancy leads to an uncertain - even poor - results.