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A GUIDE TO ANTE-NATAL TESTS: PREGNANCY TESTS
Some women know with confidence they are pregnant long before they miss their first period and often from the time of conception. Their breasts tingle and become tender; they feel sick or are more tired and sleepy than usual. Appetites and moods may change. Others suspect pregnancy, but either trust their feelings less or don't get such clear signs. Either way the first real confirmation is likely to be a missed period. For a few this can come as a complete surprise. But whatever the situation, some women will want to seek further confirmation rather than just wait for time to make them certain. There are two procedures for doing this; a physical checkup or a chemical pregnancy test. Most people rely on the second, which requires less skill to administer and is usually more reliable.
A physical check-up is not reliable until at least two weeks after a period has been missed - nor are most pregnancy tests. It normally consists of an internal examination of the cervix and uterus. In very early pregnancy the cervix becomes softer and changes colour to a deeper red or bluish-purple. The uterus increases in size and will also feel softer. In a non-pregnant woman the uterus is about the size of a small lemon. By about seven weeks in pregnancy it has increased to the size of a larger lemon* by nine weeks the size of an orange and by twelve weeks the size of a grapefruit. Breasts may also swell and the nipples and the area round them may darken and broaden. However all these signs can be misleading in early pregnancy and the most reliable and common way of checking for pregnancy is a chemical pregnancy test on a woman's urine.
Chemical pregnancy tests are based on their ability to detect the presence of a hormone called HCG, or human chorionic gonadotrophin, in urine. HCG is secreted by the embryo and is not present in the urine or blood unless a woman is pregnant. HCG tests arc normally not effective until a woman is two weeks overdue for her last period, but are then extremely simple, quick and cheap. They are known as immunological or immunoassay tests because they rely on mixing HCG with an HCG antibody substance. In a negative test the mixture coagulates; in a positive test it remains as cloudy liquid. An HCG test can either be done on a slide or in a test tube. Slide tests can give a result within a matter of minutes, but are less sensitive to lower levels of HCG and are therefore less suitable in very early pregnancy when the level of HCG may still be low. Test tubes take a couple of hours to give a result, but are better at detecting lower levels of HCG. Either system, if properly used, is relatively accurate. In about seven per cent of women HCGs fail to diagnose pregnancy. The most common reasons for this are that the test has been done too early in pregnancy or that the urine sample is too diluted (a woman has drunk too must before the test), too old or has been contaminated, often by detergent used to wash out the sample bottle. A further two per cent of women may be falsely diagnosed as pregnant. The usual reason is because a woman is using drugs, e.g. tranquillisers, anti-depressants or even aspirins. HCG tests are so simple that they are now widely available in kit form from chemists. The slide test variety are probably better for home use. Test tubes will only work if they remain undisturbed for two to six hours after the urine sample has been added.
In recent years the HCG test has been refined using radioactive chemicals. Radio-immunoassay, as it is called, is very sensitive to low levels of HCG and can therefore detect pregnancy within several days of conception. But it involves elaborate and expensive equipment which is not widely available.
Normal HCG tests should be available everywhere on the NHS, either through your GP or the local hospital ante-natal clinic. However, the increasing availability of commercial or charitable alternatives has encouraged some health authorities to cut back on pregnancy testing, and if you want a urine test you may have to insist quite firmly. Unfortunately NHS pregnancy tests almost invariably take longer to give you a result because of understaffing in the labs or because of delays in the bureaucracy involved in sending out the results, and you may have to wait up to a week. This has encouraged a growing number of women to turn to commercial or non-NHS alternatives in order to get a quick answer. The only problem is that the more women who bypass the NHS, the more the NHS is encouraged or able to downplay pregnancy testing facilities. If you can afford the alternatives that is all right, but a BPAS (British Pregnancy Advisory Service) study has shown that even minimal charges for pregnancy testing reduces the number of women who use the service. Pregnancy testing should be readily available on the NHS and results should be available immediately if only the doctors involved would do the two-minute slide test themselves. Contact your Community Health Council if you find local NHS services inadequate.
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Women's Health