Commom pregnant tests - Family - http://maxpages.com/newmomclub/commom

Can a serum pregnancy test produce a false positive?

It is very unlikely that the serum test could be wrong, as it is a direct measurement of the hCG that a pregnancy produces. Although some tumors produce hCG, breastfeeding does not.

Can measuring hCG determine gestational age and/or multiple pregnancies ?

Pregnancy tests generally measure the hormone hCG -- which is unique to pregnancy -- in the blood or urine. These tests are getting more and more sensitive and can turn positive as early as one week from conception. Although it is possible to quantify how much of this hormone is present and give a rough idea of how far along the pregnancy is, this would not be a usual use of this test.

If your test was positive sooner than you expected it to be, you may be off on your dates, but unless the exact amount of hCG is measured, it would not be indicative of a multiple gestation. If the lab did quantify the test, then twins would have more hCG than a singleton pregnancy. An ultrasound would answer the question best.

The best indications of gestational age are good dates -- knowing when you conceived -- if that is possible, and an early ultrasound. It would be very unlikely if you got pregnant on the pill, if taken correctly, unless you were on antibiotics or had vomiting or diarrhea, which would interfere with pill effectiveness.

hCG level: Should this test be routine?
By itself, human chorionic gonadotropin (hCG) levels reveal little. When done in a series, they tell us that the embryo is probably still viable and attachment within the uterus is stable. However, elevated hCG levels can occur with pregnancies destined for poor outcome as well, such as in a molar or ectopic pregnancy. The best evidence of a viable pregnancy at this stage is appropriate uterine growth, a positive pregnancy test and absence of bleeding and cramping.

With biochemical screens such as hCG, comes the risk of a falsely high or low result, which may cause needless anxiety. Furthermore, how would the knowledge of the results change the management of the pregnancy? There is nothing that can be done for the baby or the mother on the basis of only one test. Further evaluation would be needed, which would be done at greater expense. And many of these tests would ultimately be given without cause.

The levels hCG should evaluated if maternal symptoms such as bleeding, cramping or pain occur and the practitioner must decide if the pregnancy is ectopic or within the uterus. Ultrasound finding would be supplemented by hCG results.

We know that hCG levels should increase a certain amount every 36 to 48 hours, and if they do, this is reassuring. But again, this is done only in the case of bleeding or suspicion of an ectopic pregnancy.

At about 15 weeks, every woman should be offered an AFP test. Information on this test should be dispensed at your first prenatal visit. The test can tell you whether or not you may be at a high risk of having a baby with a neural tube defect such as spinal bifida. By that time, you should have received information on folic acid's role in lowering chances of neural tube defects.

Some clinics offer a triple screen, which includes an hCG level, with the addition of estriol and AFP. Such testing can help detect fetal Down syndrome. An association with Down syndrome has been established for low alpha-fetoprotein (AFP), elevated hCG and low estriol levels. The combination of all three biochemical markers, together with maternal age, can be used to calculate a specific, individual risk for Down syndrome.

An abnormal triple-screen result for Down syndrome is not predictive of Down syndrome, however. There is a need to improve the efficiency of serum screening and to more precisely identify pregnancies at high and low risk for genetic disease. The standard of care now is to recommend a targeted ultrasound study if the mother receives an abnormal triple screen or AFP result. Also, the gestational age should be checked again as incorrect dating could cause unexected results.

Normal ultrasonographic anatomy and findings significantly reduce the risk of both Down syndrome and any significant chromosome defects in pregnancies with abnormal triple-screen results.

I hope this answers your question. It is not common practice to offer an hCG test, but you should start thinking about whether or not you wish to have an AFP or triple screen at 15 to 20 weeks.

AFP

AFP is produced sequentially by the fetal yolk sac, the gastrointestinal tract and the liver. It reaches a peak concentration in fetal serum of approximately 300 mg/dl by the end of the first trimester. The fetal liver produces a constant amount of AFP through the 30th week of gestation, although levels in the fetal blood decrease as the pregnancy advances. This is best explained by a dilutional effect in the enlarging fetal intravascular compartment. After 30 weeks gestation, fetal AFP production declines precipitously.

AFP is also found in high concentrations in amniotic fluid. The decrease in amniotic fluid AFP throughout the second and third trimester closely parallels the decrease in AFP in the fetal blood. A small proportion of AFP enters the amniotic fluid after filtration of the fetal blood trough the kidney. As the fetus swallows amniotic fluid, AFP is destroyed by gastrointestinal proteolytic enzymes. AFP concentration in amniotic fluid is approximately 150 times less than in fetal serum.

In the maternal circulation, AFP levels rise until the 30th gestational week. Thereafter, levels decline until term and drop precipitously after delivery. During the second trimester, maternal serum AFP levels increase while fetal serum levels decline. This paradox is not completely understood, but may be due to the enlarging placenta allowing a greater capacity for diffusion of AFP, or changes in the permeability of the placenta to AFP. The mechanism for transfer of AFP to the maternal circulation is both transplacental (two thirds) and transamniotic (one third). A comparison of AFP levels in the maternal and fetal compartments is shown diagrammatically in Figure 1.6

Understanding Multiples of the Median

An alpha-fetoprotein test measurement is typically reported as a multiple of the median (MoM). This statistical convention was introduced by the First U.K. Collaborative Study on AFP7 as a method for participating laboratories to compare indivi

Ultrasound

Ultrasound employs sound wave transmissions at certain frequencies. To date, no adverse effects on the human embryo or fetus have been identified from exposure to energies comparable to those used for clinical sonographic examinations. Ultrasound has been used in obstetrics in various forms for 25 years. It has been rigorously tested and the research is ongoing.

At very high intensities, there is a potential for human tissue damage from heat and the formation of cavities in tissue. "Real-time imaging" (the kind of procedure used for obstetrical applications) ues low-intensity waves. The FDA limits ultrasound energy exposure to 94 milliwatts/cm2 during fetal imaging. This is a non-ionizing form of radiation exposure and, unlike many procedures and interventions, there is NO contraindication for its use during pregnancy.

Having said all this, reassuring as it sounds, there is no need for routine ultrasound in pregnancy. Too often, we learn to rely on the "toys" and lose our ability to listen to the client. I have seen dates moved, clients told they were having a boy when they actually had a girl, clients told they were having one baby and had two or vice versa, clients told to prepare for a fetal anomaly where none existed, etc.

The financial burden on clients and insurance plans is not to be overlooked. If a clinic purchases a piece of new technology, they must use it to pay for it. Then there are the necessary updates to the equipment and the purchases of newer, better models. Care providers begin to rely on the technology instead of their own hearts and hands.

If an ultrasound is indicated -- for example, with bleeding, size and dates discrepancy or no dates, to visualize for a testing procedure such as amnio or version, or many other valid indications -- I would agree that it is an indispensable tool. But for routine "screening" or so that the parents can have a picture, there is no validation for its use.

If an ultrasound is recommended, do not feel gui

Amniocentesis

What is amniocentesis?

Amniocentesis provides genetic information about the fetus (as well as information about its health and maturity) through the removal of a small sample of amniotic fluid. A needle is inserted through the pregnant woman’s abdominal wall, uterine wall and amniotic sac to withdraw fluid which contains cells that have been shed by the fetus. Those cells are then cultured and analyzed. Amniocentesis can be performed during either the second or third trimester, depending on the reason it is being done. Amniocentesis for genetic diagnosis is most commonly performed between 15 and 18 weeks’ gestation.

What does this procedure entail?

For several hours prior to the amniocentesis, the woman should drink plenty of fluids to ensure an adequate volume of amniotic fluid during the procedure. The test does not require a full bladder. An ultrasound prior to the procedure determines the fetal age, position of the fetus, location of the placenta, fetal heartbeat and the number of fetuses. An ultrasound transducer (a device which delivers the ultrasound scan) remains in place to guide the needle and prevent puncturing of the placenta, fetus and umbilical cord.

The woman's abdomen is washed with a sterile solution and sterile drapes are placed over the area. A local anesthetic is not commonly used since this requires an additional needle insertion. Approximately 15 to 30 ml (1 1/2 to 3 tablespoons) of amniotic fluid is withdrawn. Withdrawal of the fluid takes about two minutes, and the body replaces it within about 12 hours of the procedure. Care is taken when extracting this fluid to avoid contamination of the sample with maternal blood, which would invalidate the results.

Typically, women perceive the needle puncture as a feeling of pressure, usually while the fluid is being withdrawn. Fear of the needle may make the procedure seem more painful than it really is. After the procedure, women may experience mild cramping. Rest is recommended until the cr

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