What is a positive pregnancy test?
A positive pregnancy test detects the presence of the pregnancy hormone hCG (human chorionic gonadotropin) in your urine or blood. This hormone is produced by the placenta shortly after the embryo implants in the uterus. A positive test indicates you are likely pregnant.
Why did the positive line disappear after some time?
There are a few reasons why a faint positive line may disappear or become lighter after some time:
The test was read outside the manufacturer’s recommended time frame
Most pregnancy tests advise looking for a positive result within 3-5 minutes for accurate results. Reading the test after the recommended time can lead to inaccurate results as the chemicals that detect hCG can start to break down. A line may appear faint or even disappear if left sitting too long.
Not enough urine or dilution of urine
The test requires sufficient hCG concentration present in urine to detect pregnancy. Using too little urine or diluting the urine can prevent an accurate reading. The line may initially appear but fade as hCG dilutes over time. Retest with first morning urine which is most concentrated.
Low levels of hCG hormone
In very early pregnancy, hCG levels may be low and close to the detection threshold of the test. This can sometimes cause a faint line that disappears. Levels then rapidly increase. Retest in 1-2 days when hCG is higher.
Chemical pregnancy
A chemical pregnancy is a very early pregnancy loss before it can be confirmed on ultrasound. The embryo implants and hCG is produced but stops rising normally before the pregnancy progresses. This causes a positive test that later fades as hCG declines.
Ectopic pregnancy
An ectopic pregnancy is when the embryo implants outside the uterus, usually in the fallopian tube. This abnormal pregnancy often causes slowing hCG production and can lead to fading positive tests as hormone levels plateau or drop.
Test error
Manufacturing errors or faulty test strips can occasionally cause a false positive that disappears on retesting. Certain medications may also cause misleading results. Confirm with a different test brand.
When to see a doctor
See your doctor promptly if:
– The positive line completely disappears upon retesting
– You had a positive test now getting negatives
– You have signs like pain or bleeding
They can order quantitative hCG blood tests and ultrasound to determine if it is a viable pregnancy, ectopic pregnancy or miscarriage. Proper diagnosis and prompt treatment are important for your health.
Conclusion
A disappearing positive line can be distressing but does not always mean a definite miscarriage. Early or abnormal pregnancies can cause fluctuating hCG levels and faint results. Retest properly in a day or two. See your doctor right away if the line disappears on repeat testing to determine viability and next steps. With early intervention, some initially ambiguous pregnancies can still progress normally.