If you use a home pregnancy test and get a positive result, your doctor may suggest a test to find out the amount of human chorionic gonadotropin, or HCG, you have in your blood. Your body begins producing small amounts of this pregnancy hormone once the fertilized egg implants in your uterus, and continues to do so throughout your pregnancy.
Levels During Pregnancy
Your HCG levels can vary tremendously from other women, and from pregnancy to pregnancy. The amount of HCG present in your blood is not as important as the rate at which it increases, unless your blood levels are much higher or much lower than what is expected. You are considered pregnant if you have an HCG level of 25 mIU/ml. By the time you miss your period, or four weeks after your last menstrual period, your HCG level may be somewhere between 5 and 426 mIU/ml, according to the American Pregnancy Association. These levels should double every 2 to 3 days during your first trimester, though in some pregnancies, it may take up to four days for them to double. By the end of your first trimester, your HCG levels may be between 25,700 and 288,000 mIU/ml. After this time, your levels will slowly begin to fall and will throughout your pregnancy, but you may have some residual HCG for up to six weeks after giving birth.
Home Pregnancy Tests
Home pregnancy tests detect the amount of HCG in your urine. The amount of HCG needed for a positive home pregnancy test varies. Some tests can detect the minute amounts of the hormone that are present as soon as 10 or 12 days after ovulation, while others are effective only after you have missed your period. If you have a low level of HCG in your urine, you may not test positive even after you miss your period. If you think that you are pregnant but have a negative urine test, wait one week and re-test. If the test still is negative, see your doctor for a blood test.
Unexpected Results
Sometimes a very high or very low HCG level can indicate a problem. If your HCG levels are not doubling every 2 or 3 days, your doctor may order an ultrasound ensure that your baby is developing normally. In some cases, low HCG levels or a slow rate of increase can indicate a potential miscarriage. An ectopic pregnancy -- when the fertilized egg implants outside the uterus, usually in the fallopian tube -- can cause lower-than-normal HCG levels. A molar pregnancy, which causes a type of tumor in the uterus, can cause high levels of HCG; these levels may persist after the tumor is removed. High levels of HCG can also indicate a twin or triplet pregnancy.
Considerations
If you have gone through menopause, you may have a low level of HCG in your blood. If it is higher than 9.5 mIU/ml, however, then you may have not gone through menopause, and may in fact be pregnant. If you have symptoms of pregnancy after missing several periods, see your doctor to rule out pregnancy. If you have a miscarriage, your doctor may test your HCG levels several times over the following 4 to 6 weeks ensure that your HCG levels return to the normal non-pregnancy level of under 5 mIU/ml.
References
- American Pregnancy Association; Human Chorionic Gonadotropin; July 2007
- "American Family Physician"; Ectopic Pregnancy; Josie L. Tenore, M.D.; Feb. 15, 2000
- March of Dimes; Ectopic and Molar Pregnancies; August 2008
- American Pregnancy Association; Understanding Pregnancy Tests: Urine & Blood; March 2011
