Pregnancy Tests

A pregnancy test is a test to determine whether or not a woman is pregnant. more...

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Modern tests

The earliest test for pregnancy is a rosette inhibition assay for early pregnancy factor (EPF). EPF can be detected in blood within 48 hours of fertilization. However, testing for EPF is expensive and time consuming.

Most chemical tests for pregnancy look for the presence of the beta subunit of hCG or human chorionic gonadotropin in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization. Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine tests have published detection thresholds between 20 mIU/mL and 100 mIU/mL, depending on the brand. Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests. Most \"home\" pregnancy tests are based on Lateral flow technology.

With obstetric ultrasonography the gestational sac can sometimes be visualized as early as four and a half weeks of gestation (approximately two and a half weeks after ovulation) and the yolk sac at about five weeks gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as 6 weeks, and is usually visible by 7 weeks gestation.

History

The ancient Egyptians watered bags of wheat and barley with the urine of a possibly pregnant woman. Germination indicated pregnancy, and based on what type of grain sprouted they predicted the gender of the fetus. Hippocrates suggested that a woman who had missed her period should drink a solution of honey in water at bedtime. Resulting abdominal distention and cramps would indicate the presence of a pregnancy. Avicenna and many physicians after him in the Middle Ages performed uroscopy, a nonscientific method to evaluate urine. Selmar Aschheim and Bernhard Zondek introduced testing based on the presence of hCG in 1928.

In the Aschheim and Zondek test an infantile female mouse was injected subcutaneously with urine of the person to be tested, and some time later the mouse was killed and dissected. Presence of ovulation indicated that the urine contained hCG and meant that the person was pregnant. A similar test was developed using immature rabbits, the rabbit test. Here, too, it was necessary to kill the animal to check its ovaries. An improvement arrived with the frog test that was still used in the 1950s. A female frog was injected with serum or urine of the patient. If the frog produced eggs within the next 24 hours, the test was positive. In the frog test, the animal remained alive, and could be used again.

Read more at Wikipedia.org