Early Pregnancy Tests

Early pregnancy tests allow a woman to know that she has become pregnant within two weeks after conception has occurred. Using an early pregnancy test, a woman can know that she is pregnant before she has a missed period.

Development

Progress toward creation of the first pregnancy test developed from a discovery made at the Johns Hopkins University School of Medicine. In the 1930s, Dr, Georogeaana Jones, a resident at the University, discovered that human chorionic gonadotropin (hCG) was produced by the placenta. That discovery revealed the link between hCG and pregnancy.

Less than twenty years later, Rosalyn Yalow found a way to do a radioimmunoassay (RIA). Using RIA equipment and techniques, medicinal laboratories could measure the hormone levels in a great many different patients. That allowed the measurement of hCG levels in a great many women.

Then in the mid-1970s, those in the field of medical research learned about another important discovery—discovery of a way to make monoclonal antibodies. That discovery led to creation of the immunoassay. As the immunoassay began to replace the radioimmunoassay, pregnancy testing abandoned its need for large pieces of equipment.

During the performance of an RIA, a large machine is used to detect the radiation from the tested sample. During performance of a simple immunoassay, the eye detects a color change in the tested sample. For that reason, an immunoassay can be done in the home.

Women quickly responded to the availability of the home pregnancy testing kits. Yet those kits did not allow a pregnancy to be detected in its earliest stages. Creation of the early pregnancy testing kits followed the discovery that hCG was released by the zygote as it made its way to the uterus. Only after implantation of the zygote (ovum) does the placenta begin to make hCG.

Interpretation of the Results

Both the RIA and the immunoassay involve detection of a hormone. Each hormone represents one of the many proteins produced within the human body. Many of those proteins find their way into the bloodstream.

The correct interpretation of results from an early pregnancy test demands the identification of the proper protein. Early pregnancy tests measure very low hCG levels (from 100 mlU/ ml hCG down to 20 mlU/ml hCG). At such low levels, the early pregnancy test can confuse a different protein with hCG. That can lead to an incorrect interpretation of the results.

Detection of a protein other than hCG can cause a test to yield false positive results. Such results most often appear when a test subject has taken some sort of medication (usually a diuretic or premethazine). A woman also risks getting a false positive result if she chooses to ignore the expiration date on an early pregnancy test kit.

Formats for the Early Pregnancy Test

At the present time there are two primary formats for an early pregnancy test. One involves the use of a test strip. The woman who wants to know if she is pregnant puts the test strip in a container holding her urine. The second format calls for conduction of a midstream test. The woman places a test stick in a stream of her urine.

Both of those formats rely on detection of hCG. Discovery of the early pregnancy factor (EPF) could lead to development of other formats for the early pregnancy test. EPF is an immunosuppressant released by the ovary in response to release of a specific messenger chemical from the ovum. It suppresses the immune response from the mother prior to implantation of the zygote.