Testing For Pregnancy

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Any woman who has been trying to conceive for very long soon develops a love-hate relationship with pregnancy tests. Last year, consumers spent $191.0 million on home pregnancy tests (HPTs). This has increased from the previous year's figure of $180.6 million.

When a woman becomes pregnant, the pregnancy hormone (human chorionic gonadotrophin, or hCG) is produced. Home pregnancy tests detect the presence of this hormone in a woman's urine. An hCG beta blood test as administered at your doctor's office is much more sensitive than an HPT, yields a quantitative result (as opposed to the qualitative "yes" vs. "no" result of an HPT), and can detect pregnancy as early as 10 days after fertilization.

What is hCG?

Human Chorionic Gonadotropin (hCG) is the "pregnancy hormone" that keeps the corpus luteum producing progesterone when conception occurs. It is produced by the placenta during pregnancy and is measured by home pregnancy tests (HPTs). A woman "usually" produces 25 milli-international units per milliliter (mIU/ml) of hCG 10 days after conception. As a general rule, hCG beta numbers should double every two to three days. Accordingly, the concentration of hCG rises rapidly, frequently exceeding 100 mIU/ml by the first missed menstrual period and peaks in the range of 30,000-200,000 mIU/ml by 8-10 weeks into pregnancy. An hCG level of less than 5 mIU/ml generally indicates that one is not pregnant.

The appearance of hCG in urine soon after conception and its subsequent rise in concentration during early gestational growth make it an excellent marker for the early detection of pregnancy. However, if you have been given an hCG injection (Profasi, Pregnyl) to trigger ovulation or to lengthen the luteal phase of your cycle, trace amounts can remain in your system as long as 10 days after your last injection and may give a false positive on a pregnancy test. Two consecutive quantitative hCG beta blood tests can circumvent this problem; if the level increases by the second test, you are likely to be pregnant.

How do I choose an HPT?

There are two types of home pregnancy tests - mid-stream tests and those with a urine well. The mid-stream tests are basically sticks that the patient holds in her hand at one end and at the same time urinates on the other end. The test units with a urine well contain a urine collection cup and require the woman to collect urine in this cup. After collection, the patient utilizes a dropper to place the sample into a urine well on the test unit. This type tends to be more economical.

The major difference between all test kits is the degree of sensitivity to hCG. Most urine tests allow the detection of pregnancy as early as 14 days after conception in most circumstances. Some newer tests, like the First Response Early Detection, claim to detect at 11 days past ovulation (dpo), with a sensitivity threshold of 25 mIU/ml. The Lady Tester in Conceiving Concepts' Fertility Store also detects hCG at 25 mIU/ml and may actually detect lower amounts, although it may take up to 15 minutes to read. The ClearBlue Easy One Minute Pregnancy Test detects at 50 mIU/ml. Many other home pregnancy tests have a detection level of 50 mIU/ml requiring you to wait until your first missed period before you test.

You may have to experiment to find which test kit you prefer. Some tests have lines that are more difficult to interpret or may take longer to read. At Conceiving Concepts' Fertility Store, several types are offered.

Do I have to use the first morning urine?

Even if testing on the first day of a missed period, most test kits don't require first urine of the morning (as previous years' kits did). In other words, you can use urine from anytime of the day for use in the test kits. It is, however, a good idea to try to hold your urine for four hours preceding the test.

How long should it take for a result?

The test results should be read between two and seven minutes after adding the urine. The package insert will give clear directions. Throw the test away after the time has elapsed. Generally, after seven minutes the dye can break through and you may see an evaporation line, which can be confusing and disappointing.

What do I do if the test result is positive?

A positive test indicates the presence of hCG in the urine. A doctor should then be consulted to confirm the pregnancy.

What do I do if the test result is negative?

Generally, you can believe the positive, but you might get a false negative. If your period is late, test again. Many people won't have a positive HPT until the first day of a missed period. If the test is still negative and the period still hasn't started, a doctor should be consulted.

What else should I know?

Some manufacturers say that extended exposure to extreme heat may affect the reliability of the tests. Tests that spend most of the day in a metal mailbox may experience extreme temperatures that can influence the accuracy of the tests.

Finally, each test comes with a very clear set of directions and usually offers a toll-free hotline staffed by a nurse. If you have questions about your test, feel free to call that number.

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