Re: Мужчины - а вы любите детей?
exerts (sorry that in English; don't have this info in Russian)Originally Posted by Миленция
Screening for fetal Down syndrome
Measuring maternal serum alpha-fetoprotein
In cases where a low level of MSAFP is reported, it indicates the condition of Down syndrome or other chromosomal aneuploidy and failing pregnancies (Merkatz, 1984; Hsu, 1996).
Measuring maternal unconjugated estriol
The amount of estriol in maternal serum depends upon viable fetus, a properly functioning placenta, and on maternal well-being. Fetal adrenal glands produce dehydroepiandrosterone (DHEA) that gets metabolized to estriol in the placenta. Estriol crosses to the maternal circulation and is excreted either by maternal kidney in urine or by maternal liver in the bile. In the third trimester, the level of estriol gives an indication for the well-being of the fetus. A low level of estriol is an indication of Down syndrome and adrenal hyperplasia with anencephaly (Haddow, 1992; Phillips, 1992). If the estriol level drops to a great level, then it indicates risk to fetus.
Measuring maternal serum beta-human chorionic gonadotropin
Following conception and implantation of the developing embryo into the uterus, the trophoblasts produce enough beta-HCG, which is an indication for pregnancy. In the middle to late second trimester, the level of beta-HCG also can be used in conjunction with the MSAFP level to screen for chromosomal abnormalities. An increased beta-HCG level coupled with a decreased MSAFP level suggests Down syndrome (Bogart, 1987; Hsu, 1996). The beta-HCG level also can be quantified in serum from maternal blood, and, if its amount is found to be lower than expected, it indicates abortion or ectopic pregnancy. If the level of HCG is estimated to be considerably high, then it indicates the possibility of trophoblastic diseases. The elevated level of HCG, along with absence of the fetus on ultrasonography, indicates a hydatidiform mole.
Amniocentesis is an invasive, well-established, safe, reliable, and accurate procedure performed between 14-20 weeks of pregnancy. Amniocentesis is advised for pregnant women at 35 years or older for detection of chromosomal abnormalities in the fetus.
It is performed under ultrasound guidance. A 22-gauge needle is passed through the mother's lower abdomen into the amniotic cavity inside the uterus, and 10-20 mL of amniotic fluid that contains cells from amnion, fetal skin, fetal lungs, and urinary tract epithelium are collected. These cells are grown in culture for chromosomal, biochemical, and molecular biologic analyses. Supernatant amniotic fluid is used for the measurement of substances, such as AFAFP, hormones, and enzymes.
The results of cytogenetic and biochemical studies on amniotic cell cultures are more than 90% accurate. In the third trimester of pregnancy, the amniotic fluid can be analyzed for determination of fetal lung maturity. Risks with amniocentesis are rare but include 0.5-1.0% fetal loss and maternal Rh sensitization.
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