Signs and symptoms of pregnancy can be baffling for some women. Home pregnancy tests are not always reliable, and their timing is tricky. Most women believe that once they are pregnant, they do not bleed until birth, but that is not always the case. It is possible to seemingly have a period while pregnant and have a negative pregnancy test result.
Home Pregnancy Tests
According to a January 2004 "American Journal of Obstetrics and Gynecology" study, home pregnancy tests are highly inaccurate, reporting both a high number of false positive and false negative results. In fact, only 1 in 18 home pregnancy tests was able to detect a pregnancy at the time of a missed period. A more reliable option is to have a doctor do a blood test.
Timing of Tests
According to Toni Weschler, MPH, author of the bestselling book "Taking Charge of Your Fertility," pregnancy tests should be taken at least 14 days after ovulation. While a fertilized egg implants on the uterine wall approximately seven to 10 days after ovulation---meaning a woman is pregnant---it is difficult to obtain a positive test result that early.
Spotting
Some women may think they are having a period when they are actually spotting or experiencing implantation bleeding. The American Congress of Obstetricians and Gynecologists says vaginal spotting can actually be quite common and most women who experience this go on to have healthy babies. According to Weschler, implantation bleeding may resemble a very light period, though the blood is more brown than red in color. Implantation bleeding usually occurs seven to 10 days after ovulation. Both of these may occur before a woman has a positive pregnancy test result.
Molar Pregnancy
A molar pregnancy is a condition in which a mass of tissue, not an embryo, implants and grows on the uterine wall. Molar pregnancies are caused by genetic error and must be surgically removed. Often the first symptom is vaginal bleeding. According to a 2010 study in the "Singapore Medical Journal," false-negative pregnancy test results are associated with molar pregnancy.
Miscarriage
If a woman first tests positive for pregnancy and then has what seems to be a period with a negative test, she is likely having a miscarriage. Other warning signs include a gush of fluid from the vagina or passed fetal tissue. Miscarriages are often genetic. A woman should contact her doctor or midwife immediately if she suspects miscarriage, as she may require surgery.
References
- "American Journal of Obstetrics & Gynecology"; Accuracy of home pregnancy tests at the time of missed menses; L. Cole, Ph.D.; January 2004
- American Congress of Obstetricians & Gynecologists: Miscarriage and Molar Pregnancy
- "Singapore Medical Journal"; Molar Pregnancy with False Negative Urine hCG; Y. Pang, H. Rajesh; 2010
- Taking Charge of Your Fertility
