Question: Is a Lighter Colored Home Pregnancy Test Line a Sign of Miscarriage?
Home pregnancy test lines show up -- or don't -- based on the detection of the hormone
hCG in your urine. When hCG is present, the test will return a positive result for pregnancy, and when hCG is not present, the test comes back negative. Given that hCG levels
increase exponentially during early pregnancy, doesn't that mean the pregnancy test line should get darker and darker if the pregnancy is normal?
Answer:
In actuality, things are not that simple. Although a home pregnancy test line
would probably be darker when the urine has a higher concentration of hCG, taking multiple home pregnancy tests to check the color of the line is simply not a reliable method of monitoring development of early pregnancy. Blood is the far more reliable body fluid for monitoring hCG levels.
The reason is that blood maintains a fairly steady composition at all times, thus making it easier to monitor changes in chemicals such as hCG. In contrast, the concentration of urine will fluctuate heavily throughout the day based on how much fluid you drink, how frequently you use the restroom, and other factors. Less concentrated urine means a lighter colored home pregnancy test line.
Even though you will likely pass more hCG in your urine during the course of a day as the pregnancy progresses and your levels increase, this does not mean a home pregnancy test would necessarily reveal a darker line. A person in early pregnancy who takes a test with very concentrated urine could theoretically have a darker colored home pregnancy test line than someone in later pregnancy who tests after drinking multiple gallons of water.
In contrast, the levels of hCG in your blood would not be affected by external factors, and thus quantitative
hCG blood tests over a period of days are far more reliable for monitoring hCG levels. If you are feeling anxious about miscarriage or having any symptoms, don't waste money buying multiple home pregnancy tests (and if you can't fight the temptation, don't waste time worrying about light-colored pregnancy test lines). Instead, speak to a practitioner about finding some other form of reassurance that your pregnancy is progressing as it should, such as a blood test.