What's New in Pregnancy Tests?

Baby we've come a long way.

Traditionally diagnosis of pregnancy is based on missed menstrual periods, elevated temperature, feelings of nausea and breast changes. As the pregnancy progresses more visible signs and symptoms develop.

Pregnancy testing has evolved during the past half century from a time consuming, complicated laboratory procedure using expensive test animals into a rapid, relatively inexpensive and convenient technique.

The basis for most pregnancy tests involves the production of human chorionic gonadotropin or HCG by the placenta during pregnancy. It can be detected in blood or urine. In normal pregnancy the production of HCG begins within 48 hours after instantiation, ascends to a peak between 50 and 90 days after the last menstrual period then falls to a lower level throughout the pregnancy and finally ceases 3 - 10 days after delivery.

In 1928 two Germans, Aschheim and Zondek introduced the first biological test. They observed that urine from pregnant women injected into immature female mice caused changes in the ovaries. After repeated injections the test animals were killed 4 - 5 days later and the ovaries examined for evidence of HCG activity.

In 1932 Friedman did the same thing to rabbits and found that an earlier result could be obtained. The rabbits were killed and examined 48 hours later.

In 1941 Frank and Berman used immature female rats. These were killed and the ovaries examined 16 - 24 hours later.

In 1947, the male toad test was introduced. Injections of blood containing HCG caused the appearance of sperm in the toad's urine. The reporting time for the male load test was 1 - 5 hours and the same animals could be used again.

Since 1942 another avenue has been that of hormone tests. Either injected or taken orally, oestrogen-progestogen combinations will induce menstruation in the non-pregnant woman. Because of the suspicion of increased congenital malformation associated with the administration of these hormones during early pregnancy the use of these tests has been discouraged since 1975.

In 1960 the first immunological test carried out in a test tube became available Immunological tests utilise antibodies to detect HCG in blood or urine.

In 1962 a similar test was developed which could be done using a drop of urine on a slide. The agglutination of latex particles indicates HCG; This is the basis of the standard urine tests performed today in a doctor's surgery or laboratory. The result can be read in 2 minutes These tests however can only be carried out 10-14 days after a missed period.

The search for tests capable of detecting pregnancy at a much earlier stage continues. A new generation of tests called radioimmunoassays are capable of diagnosing pregnancy prior to or at the time of the first missed period. Instead of using latex particles this method uses HCG labelled with radioisotopes of iodine.

In 1974 a more rapid, one hour lest was developed at Cornell called a radio recept-orassay.

Now the good news!

This type of test is now available in Wellington. It is more expensive. It requires a blood sample, not a urine sample. It will give positive results at the time of the first missed period. It eliminates the long 14 day wait for standard tests to become positive.

Now for the bad news.

What does the Royal Commission have to say about pregnancy tests? Virtually nothing. In the terms of reference the Commission was expected to deal with "contraceptive matters in all commonly existing and likely forms". This should have included a discussion on new and future techniques for pregnancy diagnosis. The Commission has neglected to do this. Throughout the report the Commission refers to pregnancy diagnosis in terms of the standard urine lest which becomes positive at about 14 days after the missed period.

The Commission is sadly out of date before publication.

They do however make a vague recommendation regarding pregnancy tests (Pg. 197;)

"That early pregnancy testing services.... be free of cost and be made widely available."

The text does not discuss this recommendation so we do not know what it means. What is meant by Early pregnancy tests? Does that include the more expensive radiommunoassays? Would they be free? And how Widely Available should tests be Through doctors only? Through Hospital Boards? Through chemists? Through mail order? Do-it-yourself tests are available overseas.

None of these issues have been discussed by the Commission. It is ironic that in the same month that technology takes us one step forward, the Royal Commission takes us two steps backwards.

Baby we've still got a long way to go.

Margaret Sparrow