HCG Levels in Pregnancy
Contributed by Angie Boss Staff Writer
After months or
even years of fertility treatments, we breathlessly await the clinic's call or the home pregnancy test response that will
reveal whether or not the cycle was successful. The clinic's blood test or the home test measure -HCG.º Human chorionic gonadotropin,
is a hormone made by the pregnancy that can be detected in the mother's blood or urine even before the woman's missed period.
This hormone is what we look for with a "pregnancy test." HCG, which is secreted by the trophoblast after the ovum is fertilized,
appears in the blood and urine of pregnant women as early as 10 days after conception, which is one to two days after implantation.
What is HCG?
HCG serves to maintain progesterone production by the corpus luteum in the early part of pregnancy.
By the time HCG drops at the beginning of the second trimester, the placenta can make sufficient progesterone to maintain
the endometrium. HCG also stimulates the development of fetal gonads and synthesis of androgens by the fetal testes. HCG
has a similar to function to LH in stimulating secretion of estrogen and development of the placenta.
However, HCG may
also be elevated in abnormal circumstances in men as well as women.
HCG Injections and Testing
For women that
have had an HCG injection (Profasi, Pregnyl) to trigger ovulation or to lengthen the luteal phase of your cycle as part of
their infertility treatment, the hormone will take about five to 14 days to clear from the woman's system, depending on the
dose and the individual woman. This can causes problems with interpretation of pregnancy tests done earlier than 14 days after
an HCG injection. It can give a false positive on a pregnancy test. Two consecutive quantitative HCG beta blood tests can
circumvent this problem. If the level increases by the second test, you are likely to be pregnant.
Do I Need an HCG
By itself, a single test of HCG levels reveals little because the range of normal values varies a lot. Although
most do, not all doctors test HCG routinely to confirm a pregnancy. A doctor will order blood HCG tests to determine whether
an embryo or fetus is still viable under certain circumstances, including cases of an early pregnancy confirmation after IVF
or insemination; to rule out ectopic pregnancy if a woman has previously had one or is having symptoms associated with ectopic
pregnancy, such as bleeding, cramping or pain; if the fetus can't be seen in the uterus on ultrasound; or if there is vaginal
bleeding or pain.
What Do the Numbers Mean?
The problem is, once a pregnancy is confirmed, you need to know if
it progressing along normally. Keeping track of HCG numbers is one way of measuring fetal viability. HCG is measured in milli-international
units per millimeter (mIU/ml). HCG is first detectable in the blood as early as seven or eight days after ovulation by very
sensitive HCG assays. Blood pregnancy tests will be positive (> 2 mIU/ml) by 10 or 11 days after HCG injection or LH surge,
and levels vary with gestational age during pregnancy.
There is a large variation in a "normal" HCG level for any
given time in pregnancy. Caution must be used in making too much of HCG "numbers." Ultrasound findings after five or six weeks
of pregnancy are much more predictive of pregnancy outcome than are HCG levels. You won't expect to see a gestational sac
or the fetus until the HCG level reaches at least 1,200 mIU/ml.
However, a single HCG level cannot indicate a normal
pregnancy. In a normal pregnancy there is a regular increase of the HCG, so you need to see more than one value before you
can better understand what's going on. Additionally, a single value cannot always tell you how far along the pregnancy is,
because of the wide range of blood HCG levels in pregnancy. To illustrate the limitations of looking at a single measurement,
here is a sample reference list for HCG levels in singleton pregnancies, based on days past ovulation (DPO):
14 DPO, the average HCG level is 48 mIU/ml, with a typical range of 17-119 mIU/ml.
* At 15 DPO, the average HCG level
is 59 mIU/ml, with a typical range of 17-147 mIU/ml.
* At 16 DPO, the average HCG level is 95 mIU/ml, with a typical range
of 33-223 mIU/ml.
* At 17 DPO, the average HCG level is 132 mIU/ml, with a typical range of 17-429 mIU/ml.
* At 18
DPO, the average HCG level is 292 mIU/ml, with a typical range of 70-758 mIU/ml.
* At 19 DPO, the average HCG level is
303 mIU/ml, with a typical range of 111-514 mIU/ml.
* At 20 DPO, the average HCG level is 522 mIU/ml, with a typical range
of 135-1690 mIU/ml.
* At 21 DPO, the average HCG level is 1061 mIU/ml, with a typical range of 324-4130 mIU/ml.
At 22 DPO, the average HCG level is 1287 mIU/ml, with a typical range of 185-3279 mIU/ml.
* At 23 DPO, the average HCG
level is 2034 mIU/ml, with a typical range of 506-4660 mIU/ml.
* At 24 DPO, the average HCG level is 2637 mIU/ml, with
a typical range of 540-10,000 mIU/ml.
Accordingly, the key to interpreting the true value of HCG measurements is to
look at their progression. In general, the HCG level will double every two to three days in early pregnancy. Approximately
85 percent of normal pregnancies will have the HCG level double every 72 hours. However, as you get further along in your
pregnancy and the HCG levels get higher, the expected doubling time increases.
* For HCG levels <1200 mIU/ml, the
expected doubling time is 48-72 hours.
* For HCG levels 1200 to 6000 mIU/ml, the expected doubling time is 72-96 hours.
* For HCG levels >6000 mIU/ml, the expected doubling time is >96 hours.
HCG levels peak at about eight to
10 weeks of pregnancy and then decline, remaining at lower levels for the rest of the pregnancy. Here is a sample listing
of expected HCG levels based on time after conception:
* 0-1 week: 0-50 mIU/ml
* 1-2 weeks: 40-300 mIU/ml
3-4 weeks: 500-6,000 mIU/ml
* 1-2 months: 5,000-200,000 mIU/ml
* 2-3 months: 10,000-100,000 mIU/ml
* 2nd trimester:
* 3rd trimester: 1,000-50,000 mIU/ml
* Non-pregnant females: <5.0 mIU/ml
females: <9.5 mIU/ml
An HCG level that increases but is less than double the previous one
is considered abnormal and suspicious of an ectopic pregnancy. Pregnancies that are both low in level and slow to rise are
almost certain to fail. Singleton and
vanishing twin pregnancies have a wide range of acceptable HCG levels on a given
Greater-than-normal levels may indicate choriocarcinoma of the uterus, ectopic pregnancy, hydatidiform mole of
the uterus, normal pregnancy, or ovarian cancer. Once you have had an ectopic prgnancy, you have an increased risk for another,
so your HCG numbers may be monitored more carefully.
Lower-than-normal levels may indicate dead fetus, incomplete
miscarriage, or threatened spontaneous abortion. Pregnancies destined to miscarry or to be ectopic (tubal) pregnancies tend
to show lower levels (eventually), but often have normal levels initially. Some normal pregnancies will have quite low levels
of HCG ò and deliver perfect babies.
Twins or Higher Pregnancies
Twin pregnancies tend to show higher HCG levels
on a given day of pregnancy. Twin HCG levels fall within the reported range of singletons, so, you can't assume anything based
on the level alone. A higher level on a given day does increase your chances for twins, but there's no level above which you're
Your HCG Levels
Check with your physician about your own levels. In addition, do not try to
draw conclusions on either the viability of your fetus or the possibility of multiples, unless youhave a series of HCG tests
done that clearly indicate a pattern.