Pregnancy tests - whether home tests or blood tests - measure hcg levels in early pregnancy. Pregnancy tests will show a positive result if hcg is detected. Hcg stands for "human chorionic gonadotropin", which is measured in milli-international units per milliliter (mIU/ml).
When is Hcg Detected?
Hcg levels in early pregnancy can be detected approximately 11 days after conception by a blood test, and about 12-14 days after conception by a home pregnancy test, or urine test. In general, the hcg levels in early pregnancy should double every 48 hours in early pregnancy to indicate a viable pregnancy. This rate will increase to every 96 hours after a few weeks.
This doubling rate will eventually slow down as the pregnancy progresses. It peaks arounds 8-11 weeks, and then slows down and levels off for the rest of the pregnancy. After about 12 weeks of pregnancy, the placenta takes over in nourishing the baby.
If the hcg level is less than 5mIU/ml, a negative pregnancy test will result. A positive result will show with anything above 25mIU/ml.
The Rate of Increase Is What Counts For A Healthy Pregnancy!
Try not to read too much into the exact hcg numbers - it's the rate at which these numbers double that is important. Sometimes a completely healthy pregnancy will have low hcg levels in early pregnancy. An ultrasound is much more accurate than using exact hcg numbers.
HCG Levels Chart
To get a general idea of the level of hcg at various stages in early pregnancy, follow this chart:
3 weeks: 5 - 50 mIU/ml
4 weeks: 5 - 426 mIU/ml
5 weeks: 18 - 7,340 mIU/ml
6 weeks: 1,080 - 56,500 mIU/ml
7 - 8 weeks: 7, 650 - 229,000 mIU/ml
9 - 12 weeks: 25,700 - 288,000 mIU/ml
13 - 16 weeks: 13,300 - 254,000 mIU/ml
17 - 24 weeks: 4,060 - 165,400 mIU/ml
25 - 40 weeks: 3,640 - 117,000 mIU/ml
Non-pregnant females: <5.0 mIU/ml
Postmenopausal females: <9.5 mIU/ml
As you can see, the levels of hcg in early pregnancy vary quite a bit. The change in values of the numbers is more important than the actual numbers themselves.
A quantitative hcg test (done with a blood test) measures the amount of hcg in the blood. To see if these numbers are doubling at a proper rate, your doctor will give you 2 blood tests 48 hours apart if he or she is concerned that your pregnancy is at risk.
A qualitative hcg test (urine home pregnancy test) simply detects if hcg is present in the blood.
What Do Very Low Or Very High Levels Of Hcg Mean?
If low levels of hcg are detected, or if the doubling rate is too far apart, this could be a sign of miscarriage, or blighted ovum (in which the fertilized egg attaches to the uterine wall, but the embryo does not develop). This could also be a sign of an ectopic pregnancy (when the fertilized egg attaches in a place other than inside the uterus - usually a fallopian tube).
If the levels of hcg is unusually high, this could be a sign of a molar pregnancy, which is the result of a genetic error during fertilization. This would then lead to a growth of abnormal tissue in the uterus. Molar pregnancies rarely produce a developing embryo.
High levels could also be a sign of a multiple pregnancy.
Hcg After Miscarriage or Childbirth
Hcg levels after miscarriage should slowly go down, and return to a non-pregnant state. This usually takes about 4-6 weeks after a miscarriage or delivery of a healthy baby. This varies according to the situation - miscarriage, D&C or delivery of a healthy baby. This also depends on how high the levels were at the time. The further along the pregnancy was, the longer it will take for levels to go back to non-pregnancy level (<5.0mIU/ml ).
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