Pregnancy Tests

Pregnancy Test Qualitative - Blood

HCG is a hormone that is produced by the placenta. It is detectable in the blood and urine within 10 days of fertilization, or conception. After the fertilized egg implants, or attaches, to the inside of the uterus or other structure inside the mother, the levels of HCG rise rapidly. The levels continue to increase throughout the first trimester of pregnancy and reach a peak 60 to 80 days after the fertilized egg implants.

HCG is thought to be important in converting the normal corpus luteum into the corpus luteum of pregnancy. The corpus luteum is a hormone-secreting structure that grows on the surface of the ovary after ovulation takes place. In pregnancy, functions of the corpus luteum include: promoting the growth of the fetus through the 12th week of pregnancy. stimulating the development of fetal sex organs. promoting the synthesis of male hormones by the fetal testes.

Because HCG is produced by the placenta, the presence of HCG in a woman's blood indicates that she is most probably pregnant. HCG is produced regardless of the site of implantation of the egg in pregnancy. Usually this occurs within the uterus, but may happen outside the uterus, which is called an ectopic pregnancy. HCG in the blood may also be a sign of other conditions discussed below.

This test may be done to confirm or rule out pregnancy. Women of childbearing age who have been having sex should be screened with some type of HCG test if they are having the following symptoms: delayed menstrual period breast tenderness pelvic pain irregular spotting or bleeding nausea or vomiting. This test can only give a "yes" or "no" answer as to whether or not HCG is present. If the answer is "yes" the woman is most likely pregnant. This test is part of most home pregnancy test kits.

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Pregnancy Test Quantitative - Blood

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. 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: 3,000-50,000 mIU/ml
* 3rd trimester: 1,000-50,000 mIU/ml
* Non-pregnant females: <5.0 mIU/ml
* Postmenopausal females: <9.5 mIU/ml

Abnormal Numbers:
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 day.

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 guaranteed twins.

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.

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