How do pregnancy tests work?
Pregnancy tests are designed to test either urine or blood for a hormone called human chorionic gonadotropin (hCG).
Here’s how it works: During conception, the sperm fertilizes the egg in the fallopian tube and then makes its way toward the uterus. It takes an average of 9 days for the fertilized egg to implant in the woman’s uterine wall.
About 6 days after implantation, a woman’s body will start producing hCG as the placenta develops. The further along you are after conception and implantation, the more hCG is found in your blood and urine.
What types of pregnancy tests are there?
Urine tests simply test for the presence of hCG. If the hormone is present in your urine, the test will show a positive result. When used according to the directions, urine tests can be extremely accurate, depending on the amount of time that has passed since implantation and the stage of your menstrual cycle.
Blood tests also test for the presence of hCG, but in-depth blood work analysis can measure the specific hormone levels to indicate the possibility of twins or pregnancy complications. Pregnancy can be detected earlier through a blood test, as soon as 6 days after ovulation, but results from a blood test take longer to process than urine tests.
How soon can a home pregnancy test detect a pregnancy?
With some at-home pregnancy tests, pregnancy can be detected before your missed period or as little as 10 days after conception.
However, for the most accurate results, you should wait until after you miss your period to take a test.
When is the best time to take a pregnancy test?
Generally, the best time to take an at-home pregnancy test is first thing in the morning when you still have a full bladder. This ensures your urine is concentrated for a more accurate reading.
If you can’t use your test in the morning, it’s best to wait at least 3 hours from the last time you urinated to use a pregnancy test, though some tests are sensitive enough to detect hCG at any time.
How accurate are home pregnancy tests?
Many at-home pregnancy tests like Clearblue and First Response claim to be quite accurate—up to 99%. However, it depends on how and when you use the test. If you haven’t yet missed your period or have just missed it recently, you may still get a negative test result, in which case you should test again in a week if you believe you truly are pregnant.
It’s also important to ensure you follow the exact directions for your test, including reading your test after the correct amount of time has elapsed.
Could a negative pregnancy test result be wrong?
It’s definitely possible to get a negative pregnancy test result and still be pregnant for several possible reasons.
- First and foremost, improperly using the test could cause a negative result. You must follow the instructions included with your test for the highest degree of accuracy.
- Additionally, you may receive a false negative result if you take the test too soon after becoming pregnant, so be sure to always refer to the test instructions on how long to wait.
- Taking a pregnancy test later in the day may also cause a false negative, as your urine may not be concentrated enough to pick up on the elevated hCG level in your body.
- Certain medications, drugs and extremely high levels of protein can also skew results.
Could a positive pregnancy test result be wrong?
Although quite rare, there are a few reasons you may get a false positive reading on an at-home pregnancy test.
Elevated hCG levels on a pregnancy test when you’re not pregnant could be caused by any of the following:
- A recent miscarriage or abortion, in which your levels haven’t had time to go back to normal yet
- Fertility medication that contains hCG
- Certain medical conditions, such as ovarian cysts
- Menopause
In other cases, you may technically be pregnant though the pregnancy may be unviable. This may be due to ectopic or chemical pregnancies, in which your hCG levels will be elevated as seen in a normal pregnancy, thus causing the positive test result.
User error is another way to get a false positive pregnancy test result. While rare, evaporative lines may show up after the suggested time frame for reading your test result has passed, also causing a false positive.
Is there anything I shouldn’t do before a pregnancy test?
When taking a pregnancy test, you will want to do so with a full bladder. The best time to have a full bladder for your pregnancy test is first thing in the morning.
However, you should not drink large amounts of water to quickly fill your bladder, as this could cause your urine to be diluted and prevent hCG levels from registering correctly on your test.
Also, it’s sometimes recommended to wait until after your missed period to take an at-home pregnancy test to ensure more accurate results. Some home pregnancy tests do claim accuracy even before a missed period, but testing too early may cause a false positive reading.
Can I reuse a pregnancy test?
At-home pregnancy tests are considered accurate for 1 use only and should be discarded after use. After urinating on the test stick, a chemical reaction occurs to detect hCG levels in your urine.
This chemical reaction cannot be replicated using an already-used pregnancy test. You will need a fresh new test to try again, and used tests should be disposed of after the recommended time for reading the test has elapsed.
What should I do after getting a positive pregnancy test result?
After getting a positive pregnancy test reading, you should prepare yourself for the pregnancy journey. Start by calling your OB-GYN and scheduling your first prenatal appointment. Be sure you’re taking care of yourself with a healthy lifestyle, avoiding things such as alcohol and tobacco and getting the nutrients that you and a growing fetus need.
Contact All About Women Obstetrics & Gynecology
If you’ve recently found out you’re pregnant and live in the Gainesville or Lake City area, schedule an appointment with the compassionate OB-GYNs at All About Women Obstetrics & Gynecology. We can answer questions and give you advice, whether you’re pregnant or not. Learn all about pre-pregnancy checkups and other women’s care topics by browsing our knowledge center.
