A GUIDE TO ANTE-NATAL TESTS: BLOOD TESTS
A sample of your blood will normally be tested for the following: blood group, rhesus factor, syphilis, rubella antibodies, anaemia and possibly hepatitis B (also known as Australian antigen). Some of these tests, such as the one to identify your blood group, are valuable in case you need a blood transfusion. Others may be less so.
The rhesus factor, or Rh factor, is a substance in the blood. People who have it are called Rh positive; those who don't, Rh negative. Blood from one group cannot be given to the other. Rh-negative women may have particular problems in a second pregnancy if this characteristic is not picked up and treated in the first. This is because at childbirth a woman's blood may get intermixed with a small amount of foetal blood as the placenta breaks away from the wall of the uterus (or if she tears or is cut). If the baby is Rh positive, this will cause the maternal blood to generate Rh-positive antibodies. These antibodies will remain in the blood and in a second pregnancy may attack and destroy red blood cells in a new Rh-positive foetus, causing anything from severe foetal anaemia to retardation and even stillbirth. When this happens, early delivery, exchange transfusion after birth or even a foetal blood transfusion may be necessary. To prevent it, Rh-negative women are usually given an injection of a substance called anti D gamma globulin within seventy-two hours of giving birth.
Another reason for analysing a pregnant woman's blood is to check for infections in the blood stream which could cross the placenta, enter the foetal bloodstream and damage the foetus.
In Britain ante-natal clinics routinely screen only for German measles and syphilis. Some may screen for hepatitis B. Other possibly dangerous infections are thought to be sufficiently rare among women of reproductive age in this country not to warrant a routine screen. Although all these infections can easily be detected in a woman's blood, they can also easily be missed if they are not specifically being looked for. If you have reason, you should make a special request.
Anaemia is checked for by blood test early in pregnancy because it is believed that a growing foetus will take large quantities of iron from its mother and that, unless her diet is extremely good, this can leave both her and the foetus anaemic. However, the relationship between pregnancy and iron levels is not well understood and has led to the almost routine prescription of iron supplements to all pregnant women with little consideration of the benefits or risks. Over the years what is considered a normal level of iron in the blood has risen from around 9 grams per 100 ml of blood to about 10.7 grams. But this figure could be too high and some doctors prefer to put it at nearer 10 grams. The benefits of iron supplements are equally uncertain. Some doctors have suggested that it is important to build up iron stores in the foetus because it will get very little iron in a primarily milk diet during the first six months of life. Others have argued that unless there is a clear case of anaemia the value of iron supplements remains doubtful and its routine use can create problems of its own, possibly lowering resistance to infection. It is an area in which, because of lack of knowledge, it is impossible to give clear guidance.
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Women's Health
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UNDERSTANDING THE MENOPAUSE: THE PERI-MENOPAUSAL CYCLE
During the fertile years there is a gradual depletion of ovarian follicles, and hence the egg cells they contain. This process generally becomes more rapid from the age of 35. At the menopause only a few eggs remain. With the depletion of the follicles, the level of fertility is reduced and oestrogen deficiency begins. As the number of granulosa cells in the follicles reduces, inhibin production also decreases, very gradually. The level of follicle-stimulating hormone therefore changes little.
By the early forties the number of granulosa cells has decreased to such a degree that the level of inhibin they secrete will have fallen to a critical point; the level of follicle-stimulating hormone now rises. Although the menstrual periods may still be completely regular and no menopausal symptoms are being experienced, the rising follicle-stimulating hormone level represents the beginning of the peri-menopause.
As follicle depletion continues over the next few years the level of follicle-stimulating hormone will fluctuate, causing the menstrual cycle to become irregular. The amount of menstrual flow also alters, being sometimes lighter and sometimes heavier. By now the follicle-stimulating hormone will be approaching, or have reached, the point at which the peri-menopause can be said to have begun. Conception is now unlikely to happen. Oestrogen production usually remains near-normal in the early years of the peri-menopause, therefore symptoms associated with oestrogen deficiency, such as hot flushes and vaginal dryness, will not yet be evident. As oestrogen levels fall over the next few years the occasional hot flush, increasing tiredness and perhaps dizziness will occur, and menstrual periods may become more irregular with episodes of heavy bleeding.
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Womens health
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