Since getting pregnant is the single most important thing for women trying to conceive, the two week wait before taking a pregnancy test can be excruciating. It doesn't help that the signs of pregnancy can be similar to the signs of getting a menstrual cycle. During this time it is common to question every symptom, or non-symptom, and have a deep desire to know if pregnant or not. In this blog post, we answer the most common questions women have about pregnancy tests including how soon you can take a test and how you can get a false positive.
What is the earliest I can take a pregnancy test?
Most at home pregnancy tests on the market can tell you 4 days before your expected period start day if you are pregnant or not. For reasons we will discuss below, it may be better to wait until at least a day after your expected period start date to avoid a false-negative, confusion or unnecessary pain if you experience a chemical pregnancy.
When is the best time to take a pregnancy test for an accurate result?
“Patience is an emotionally freeing practice of waiting, watching and knowing when to act” - Judith Orloff, M.D
Patience is not a word couples trying to conceive want to hear or read, but being patient in this case may help reduce confusion and potentially unnecessary grief. If you wait until after a missed period, you may spare yourself grief from not being able to read the test correctly or having a chemical pregnancy.
Many health professionals believe that early tests are causing "unnecessary grief." A chemical pregnancy is one that ends naturally before 5 weeks and before are visible via ultrasound. Chemical pregnancies are common and mainly due to chromosomal issues. The only evidence that an early pregnancy existed is the measurement of hCG in a woman’s blood or urine (source).
That said, if used correctly, the newer pregnancy tests on the market tend to be accurate and can reliably let you know a couple of days before your anticipated period (granted that you have a regular cycle).
What if I have irregular cycles or don't know when my period should start?
If you have irregular cycles or you don't know when you cycle should start, one method is to count 36 days from the start of your last menstrual cycle or four weeks from the time you had intercourse.
If you suspect that you are pregnant but the test is negative you can wait a few more days and take another test or call your doctor for a blood test (source).
What do pregnancy tests measure?
At home pregnancy tests measure a hormone called human chorionic gonadotropin (hCG). This hormone, hCG, is a marker for implantation and is made right after a fertilized egg attaches to the wall of your uterus. If you're pregnant, levels of hCG continue to rise rapidly, doubling every 2 to 3 days.
When is the best time of day to take a pregnancy test?
Follow the instructions included in the pregnancy kit you purchased, but typically first thing in the morning is best. Your hCG levels are highest first thing in the morning.
What hCG levels indicate a pregnancy?
Anything above 25mIU/ml is considered positive for pregnancy. You can see the chart here for levels of hCG by week after a last menstrual period.
Typically, the hCG levels will double every 72 hours. The level will reach its peak in the first 8-11 weeks of pregnancy and then will decline and level off for the remainder of the pregnancy (source).
When does Implantation occur?
The hCG hormone appears when implantation occurs. The time it takes for a fertilized egg to implant in the uterus varies from woman to woman. On average, implantation happens about 6- 12 days after fertilization (source).
How to get the most accurate result from a home test?
The American Pregnancy Association advises women to wait until the first day of their missed period (approximately two weeks after conception) before attempting to take a home pregnancy test. As mentioned above, taking pregnancy tests early—or incorrectly—increases the likelihood of an inaccurate reading.
Wait at least a week after a missed period
Test first thing in the morning
Look for tests that are able to detect 12.4 mIU/ml hCG
Check the expiration date of the test
Follow the instructions carefully
If the line is faint, does it mean I’m pregnant?
In nearly every case, if you get a positive result, you are pregnant no matter how faint the line, color or sign is If your test uses lines or colors. If the line is very faint, wait several days to a week and test again or see your doctor for a blood test.
There are some rare cases where a false-positive can occur (see below).
When can you get a false-positive?
False positives, or when a test says you are pregnant and you are not, are very rare but certain drugs and medical conditions can cause a false-positive. Sometimes, a faint-colored second line will appear. This line may represent an early pregnancy or it may be an evaporation line. It’s probably an evaporation line if the line is completely colorless.
You could have a false-positive result if blood or protein is present in your urine. And certain drugs, such as fertility medications (ie: hCG trigger shot), anti- anxiety medications, antipsychotics, tranquilizers, anti-convulsants, hypnotics, and diuretics, may also cause false-positive results.
Rarely, certain medical conditions, such as urinary tract infection, ovarian cysts or cancer can cause a home pregnancy test to give a false positive.
Is it possible to get a false-negative?
If done too early, the test can not pick up enough hCG present in the urine to obtain a positive result. It is not uncommon to inaccurately estimate your day of expected period because we all can experience considerable inter-cycle differences. Cycles can vary by more than 13 days in 30% of women (source). Also, variations in time to implantation can impact the test results.
You are most likely not pregnancy if you get a negative result. You may be pregnant however if the following occurred:
The test is past its expiration date.
You took the test the wrong way.
You tested too soon.
Your urine is too diluted because you drank large amounts of fluids right before the test.
You are taking certain medications, such as diuretics or antihistamines.
Recommended Reading: read this blog post while you are trying to conceive on preconception guidelines to reduce changes of a miscarriage and other risks.