A: You may be pregnant and just didn't have a high enough level of hCG to trigger the test within the usual time frame. Or that test may react over time, so you really need to test again either way in order to be sure of the result. Some brands indicate that an "evaporation line" will appear if the test is left to sit. Generally speaking, you should not rely on any positive result that does not show up within the time limit stated in the test instructions. All brands have the possibility of an evaporation line or chemical line.

If you think the result is incorrect, or if it is difficult to detect a line, repeat the test after 2 -3 days with a new test.

Q: Is it possible to receive a false positive?

A: Yes. Certain fertility medications with hCG (Novarel, Profasi, Pregnyl, Humegon™, APL) and certain rare medical conditions can result in a false positive result.

Using the test within 8 weeks of giving birth or having a miscarriage may also cause a false positive result. The test may detect hCG still in your system from a previous pregnancy You should ask your doctor for help in interpreting the result of your test if you have recently been pregnant.

Factors which should NOT affect the test result include alcohol, analgesics (pain killers), antibiotics, birth control pills or hormone therapies containing clomiphene citrate (Clomid or Serophen).

Q: Can I be pregnant and not get a positive HPT?

A: Yes. Most women will register on HPTs by the time they are a few days late for a period, but not everyone will. Factors that may result in a false negative are:

• Inaccuracies in timing of the test or carelessness in the test procedure itself. Read the instructions carefully.
• Test was stored improperly. Don't store the test at extreme temperatures.
• Using a diluted urine sample. Use first morning urine.
• Taking the test too early in pregnancy. Conception does not always occur the same day that sexual intercourse has taken place.

Q: Do oral contraceptives/birth control pills interfere with home pregnancy test results?

A: No. The hormones in the pill don't cause a false positive or a false negative result.

All content written and copyrighted © Julie Snyder. Permission to republish granted to Pregnancy.org, LLC.