Diagnostic Test

Pregnancy Test (Human Chorionic Gonadotrophin)

Type of test: Blood; urine

All pregnancy tests are based on the detection of HCG, which is secreted by the placental trophoblast after the ovum is fertilized. HCG will appear in the blood and urine of pregnant women as early as 10 days after conception. In the first few weeks of pregnancy, HCG rises markedly, and serum levels are higher than urine levels. After about a month, HCG is about the same in either specimen.

• Immunologic test (agglutination inhibition test (AIT) (blood and urine)

Immunologic tests are performed by using commercially prepared antibodies against the HCG molecule. With the development of monoclonal antibodies, immunoassays can identify very small levels of HCG, and pregnancy can be detected 3 to 7 days after conception. Several immunologic tests are now commercially available for testing by the public.

• Radioimmunoassay (RIA) (serum)

The RIA is a highly sensitive and reliable blood test for the detection of beta unit of HCG. This study requires a blood sample; however RIA also may be performed with a urine test. This test is so sensitive that pregnancy can be diagnosed before the first missed menstrual period.

• Radioreceptor Assay (RRA) (serum)

The RRA for serum HCG is highly sensitive and accurate. The major advantage of this study is its reliable diagnosis of early gestation in patients requesting an early termination of pregnancy and in cases in which infertile couples are anxious to confirm pregnancy.




Human Placental Lactogen (Human Chorionic Somatomammotropin)

Type of test: Blood

The human placenta produces several hormones that are homologous to hormones of the anterior pituitary. Not surprisingly, hPL demonstrates both lactogenic and growth stimulating activity. Serum levels of hPL rise very early in normal pregnancy and continue to increase until a plateau is reach at about the 35th week after conception. Assays for maternal serum levels of hPL are useful in monitoring placental function. Measurements of hPL also are used in pregnancies complicated by hypertension, proteinuria, edema or possible miscarriage.



References:

http://www.labtestsonline.org/understanding/analytes/hcg/test.html
http://www.netlib.org/benchmark/hpl/
http://www.ovulation-calculator.com/files/hcg.gif
Diagnostic and Laboratory Test Reference by Mosby's

PLACENTA

The Placenta arises out of trophoblast tissue. It serves as the fetal lungs, kidneys and gastrointestinal tract and as a separate endocrine organ throughout pregnancy. Its growth parallels that of the fetus, growing from a few identifiable cells at the beginning of pregnancy to an organ 15 to 20 cm in diameter and 2 to 3 cm in depth at term. It covers about half the surface area of the internal uterus.


Endocrine Function
Aside from serving as the source of oxygen and nutrients for the fetus, the outer layer of the chorionic villi develops into separate, important hormone-producing system.


Human Chorionic Gonadotropin
The first hormone produced, hCG, can be found in maternal blood and urine as early as the first missed menstrual period through about the 100th day of pregnancy. Testing for hCG after birth can be used as proof that all of the placental tissue has been delivered. The purpose of hCG is to act as a fail-safe measure to ensure the corpus luteum of the ovary continues to produce progesterone and estrogen. hCG also may play a role in suppressing the maternal immunologic response so that placental tissue is not rejected. Because the structure of hCG is similar to that of leutinizing hormone of the pituitary gland, if the fetus is male, it exerts an affect on the fetal testes to begin testosterone production.


Relaxin
In females, their body produces a hormone called relaxin, it is produced by the corpus luteum, which is responsible for the softening of the ligaments in the pelvic area and other joints. This hormone helps the baby to pass through the pelvis during birth. As a result, these joints move more during and just after pregnancy.It rises to a peak within approximately 14 days of ovulation and then declines in the absence of pregnancy resulting in menstruation. During the first trimester of pregnancy levels rise and additional relaxin is produced by the decidua. Relaxin's role in human pregnancy remains under investigation, as in humans its peak is reached during the 14 weeks of the first trimester and at delivery.


Human Placental Lactogen (Human Chorionic Somatomammotropin)
hPL is a hormone with both growth-promoting and lactogenic properties. It is produced by the placenta beginning as early as the 6th week of pregnancy, increasing to a peak level at term. It can be assayed in both maternal serum and urine. It also serves the important role of regulating maternal glucose, protein, and fat levels so that adequate amounts of these nutrients are always available to the fetus.



References:
http://www.marchofdimes.com/professionals/14332_1154.asp
http://en.wikipedia.org/wiki/Placenta
http://info.med.yale.edu/obgyn/kliman/placenta/articles/Plac%20Hormones.html
http://www.birthgreeter.com/images/Placenta_1.jpg