What you should know about how pregnancy tests work
Pregnancy has always been big news, which is why most women want to know as soon as possible if they are having a baby. In the past, determining pregnancy was tricky at best. In ancient Egypt, for instance, women were encouraged to urinate on barley grain. If the barley sprouted, it was considered a ‘positive’ pregnancy test. In the middle ages, they were a little bit less efficient with renowned uromancers, or prophets who could divine whether or not a woman was with child based on how leaves or a nail reacted to her urine. While this sounds similar to the tests of today, uromancers were not known to be accurate.
Fortunately, we’ve come a long way from dipping leaves in urine, although some myths and wives' tales still persist about how to tell whether a pregnant woman is carrying a boy or a girl. The first home pregnancy test was developed in the 1970’s and, now, they are so accurate that most doctors won’t even run a second laboratory test. Here’s what you need to know about modern pregnancy tests.
Taking a Home Pregnancy Test
While there are a few variations, most pregnancy tests are about the same. The test usually comes in the form of a stick. A portion needs to come in contact with the woman's urine. After the test has made contact, it takes several minutes for the test to show a result.
When it comes to reading the result, the test varies. Some tests indicate ‘pregnant’ or ‘not pregnant’, while others have a plus or minus sign. Fortunately, the instructions for reading the test are simple and either on the box or in the instructions inside the box. While you may be excited about the test, you definitely want to hold onto the instructions while you wait.
The Pregnancy Hormone
During pregnancy, humans release the human chorionic gonadotropin hormone or hCG. This hormone is produced after sperm meets egg, but the levels double around six to 12 days after conception. At this point, the embryo has implanted in the uterus, which is what triggers the spike in this hormone’s production.
The role of hCG is to support the functions of the corpus luteum, which is a temporary structure within the ovary. The corpus luteum is a temporary structure that is created every month, or so, when the ovum releases an egg. The purpose of the corpus luteum is to prepare the body for pregnancy. Should the pregnancy not occur, the corpus luteum disintegrates and is rebuilt during the next cycle.
If conception does occur, the corpus luteum begins to produce important hormones including estrogen and progesterone. The proper production of hormones helps ensure that the uterus is ready for implantation to help the development of the fetus.
The human chorionic gonadotropin hormone is eliminated from the body via urine, which is where it can be detected by pregnancy tests.
Detecting the Pregnancy Hormone
The pregnancy test use strips that have been enriched with proteins called antibodies. Antibodies are present in the human body and serve a variety of functions. The antibodies within a pregnancy test are specifically designed to bind to hCG. The most advanced tests, such as First Response, rely on high sensitivity of the antibodies in order to detect pregnancy as early as possible.
Once bound to hCG, the antibodies produce an enzyme which, in turn, triggers a reaction in the strip. The result of the reaction depends on the nature of the strip. For instance, some of the earliest at-home pregnancy tests had the strip turn pink if the test was positive. With these tests, the enzymes triggered a dye. If you hear about the “strip turning pink” in movies, they’re referring to these types of tests.
Now, of course, there are tests that provide a digital response. The basic process, however, has not changed.
When to Take the Test
Experts recommend waiting at least one to two weeks after you’ve had sex to take a pregnancy test because the hCG hormone levels need to be high enough to be detected by the antibodies.
Some Tips While You Wait
If you suspect that you are pregnant, you may want to start preparing before the test, and thinking about what you'll do if your test comes back postitive.
- Come up with a plan for both scenarios. This can be an emotional time, which is why you also want to invest the support of your partner and even loved ones
- Avoid smoking and alcohol. These can harm a fetus, especially early on during pregnancy
- Start checking labels to ensure that you are not consuming foods or medications that are contraindicated for pregnant women.
- Speak to your healthcare providers and let them know that you think that you might be pregnant or that you are trying to get pregnant.
The wait can be difficult but, fortunately, the test is highly reliable.
Sources — CompoundChem, Healthline
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