The HCG level usually rises as pregnancy progresses, doubling every 48-72 hours until 11-12 weeks of the pregnancy. HCG or Human Chorionic Gonadotropin is the pregnancy hormone which is produced by the placenta and is detected with pregnancy tests.
HCG stands for "Human Chorionic Gonadotropin," the pregnancy hormone which is produced by the placenta and enters the blood soon after implantation and is detected with pregnancy tests. HCG is being produced by the placenta and enters the blood stream as soon as implantation happens, about one week after fertilization and ovulation, when the embryo implants and the placenta attaches to the uterine lining.
hCG under 5 mIU/ml: Negative. Not pregnant
hCG between 5-25 mIU/ml: "Equivocal". Maybe pregnant maybe not. Repeat test in a couple of days
One single hCG value does not tell you much about the viability of the pregnancy and there is a wide range of normal hCG levels in pregnancy. A normal hCG rise over several days prior to 6 weeks of the pregnancy usually indicates a viable pregnancy. In general, the best indication of a healthy pregnancy other than a normal rise of hCG is a good fetal heartbeat after 6-7 weeks.
It's main function is to support the corpus luteum producing progesterone when conception occurs. hCG can be detected both in the urine and in the blood. In blood it's detected several days earlier than in the urine.
The blood hCG test measures the HCG quantitatively, which means you get a number for the test, and the units measured are usually mIU/mL.
hCG is measured in milli-international units per milliliter (mIU/ml)
Blood hCG levels are not very helpful to test for the viability of the pregnancy if the hCG level are above 6,000 and/or after 6-7 weeks of the pregnancy. Instead, to test the health of the pregnancy better, a sonogram should be done to confirm the presence of a fetal heart beat. Once a fetal heart beat is seen, it is not recommended to check the pregnancy viability with hCG levels.
Urine hCG levels are usually lower than serum (blood) hCG levels.
Blood hCG testing is much more sensitive than a urine HPT. This means that the blood test can detect pregnancy several days earlier than the urine test, as early as 2-3 days after implantation or 8-9 days after fertilization.
Urine tests measure the urine HCG qualitatively, which means that the HPT results are either "positive" or "negative." Around the time of the first missed period (14+ days after ovulation), over 95% of HPTs are usually positive.
About 85% of normal pregnancies will have the hCG level double every 48 - 72 hours. As you get further along into pregnancy and the hCG level gets higher, the time it takes to double can increase to about every 96 hours.
Caution must be used in making too much of hCG numbers. A normal pregnancy may have low hCG levels and deliver a perfectly healthy baby. The results on an ultrasound after 5 - 6 weeks gestation are much more accurate than using hCG numbers.
An hCG of less than 5 mIU/cc is usually negative, over 25 mIU/cc usually positive, between 5 and 25 mIU/cc it's "equivocal" which simply means we don't know.
hCG levels are also higher in women carrying a female fetus when compared to women carrying a male fetus, so it is possible that the pregnancy test becomes positive later in women carrying a male fetus (click here for more information about this topic).
A transvaginal ultrasoundshould be able to see at least a gestational sac once the hCG levels have reached between 1,000 - 2,000mIU/ml. Because levels can differentiate so much and conception dating can be wrong, a diagnosis should not be made by ultrasound findings until the level has reached at least 2,000.
A single hCG reading is not enough information for most diagnoses. When there is a question regarding the health of the pregnancy, multiple testings of hCG done a couple of days apart give a more accurate look at assessing the situation.
hCG levels should not be used to date a pregnancy since these numbers can vary so widely. There are two common types of hCG tests. A qualitative hCG test just looks to see if hCG is present in the blood. A quantitative hCG test (or beta hCG) measures the amount of hCG actually present in the blood.
Other than for the diagnosis of pregnancy, hCG is also often monitored over time for reasons such as monitoring after a miscarriage, monitoring an ectopic pregnancy, and after a condition called "H.mole."
The first detection of hCG in the blood depends on when implantation happens. Extremely sensitive tests which are not available in a regular laboratory can detect the hCG even before implantation. But with regular laboratory hCG tests, hCG is usually found in sufficient levels as early as 2-3 days after implantation.
Implantation happens as early as 6 days after ovulation/fertilization (usually about 9 days after ovulation), so blood hCG can be found as early as 8-9 days after ovulation/fertilization. Pregnant women usually attain blood serum concentrations of at least 10-50 mIU/cc in the 7-8 days following implantation.
An equivocal test of between 5 and 25 mIU/cc requires a repeat within 2-3 days. If if goes higher then that's a good sign, but if it goes lower or stays about the same then that's a sign that the pregnancy has failed
HCG monitoring is useful to assess the pregnancy before the fetal heart is seen (before 6-7 weeks after LMP), ususally to rule out an ectopic pregnancy or an early miscarriage
In an ectopic pregnancy, hCG increases at lower rates than in a normal pregnancy
In a noviable pregnancy it also rises slower
At hCG levels above 1,000-1,500 mIU/ml, vaginal sonography usually identifies the presence of an intrauterine pregnancy
Within the first 2-4 weeks after fertilization, hCG usually doubles every 48-72 hours
An increase of 60% in 48 hours is still considered normal
Below 1,200 mIU/ml, hCG usually doubles every 48-72 hours
Between 1,200 and 6,000 mIU/ml serum, the hCG usually takes 72-96 hours to double
Above 6,000 mIU/ml, the hCG often takes over four days to double
More than two in three normal pregnancies have a doubling of the hCG every 72 hours
There is a wide variation of normal hCG levels. An hCG that does not double every two to three days does not necessarily indicate a problem
A maximum level is usually reached by the 10th or 11th week.
After 10 weeks or so, hCG normally decreases
Normal hCG values vary up to 20 times between different pregnancies
A single hCG value doesn't give enough information about the viability of the pregnancy
Pregnancies that will miscarry and ectopic (tubal) pregnancies are likely to show lower levels and slower rises, but often have normal levels initially
Some normal pregnancies will have quite low levels of hCG -- and deliver perfect babies
Once fetal activity has been detected by ultrasound in a normal patient population, chances of normal delivery are about 95%
Normal levels of hCG can vary tremendously. After 5-6 weeks of pregnancy, sonogram findings are much more predictive of pregnancy outcome than are HCG levels. Once the fetal heart rate is seen, most doctors will monitor the fetal heart rate rather than drawing hCG
After hCG injections (Profasi, Pregnyl) to trigger ovulation or to lengthen the luteal phase, trace amounts of hCG can remain in the body as long as 14 days or longer after the last hCG injection. This may give a false positive on a pregnancy test.
Two consecutive quantitative hCG beta blood tests can determine whether the hCG is from an injection or pregnancy. If the hCG level increases by the second test, you are likely pregnant