Why is it more common for doctors to recommend amniocentesis and cvs for women over the age of 35?

The age of 35 years was established to offer invasive techniques, because at this age the risk of secondary abortion was balanced by the technique and the risk of chromosomal alteration.

Explanation:

The possibility of early diagnosis of fetal anomalies of various kinds (neural defects, chromosomopathies, etc.) has been one of the top concerns of gynecologists and geneticists, for obvious reasons.

Throughout these years, prenatal diagnostic techniques have been developed that allow therapeutic decisions by doctors or viability of pregnancy by parents. These techniques are initially performed with non-invasive methods (biochemical determinations, ultrasound), and if the suspicion is increasing, it is passed to more invasive techniques such as amniocentesis or chorionic villus biopsy.

Given that in the latter there is a risk of loss of pregnancy, it is previously attempted to ensure that the indication is correct, and for this, new biochemical tests and risk calculation systems have been added.

Until recently the criterion for establishing the risk of fetal chromosomal abnormality was the mother's age, since there was a clear relationship between maternal age and chromosomal abnormalities, especially Down. The age of 35 years was established to offer invasive techniques, because at this age the risk of secondary abortion was balanced by the technique and the risk of chromosomal alteration. The problem was that a small number of cases were detected. Therefore, other parameters have been sought that estimate more precisely those subsidiary chaos of early detection.

The estimation of the risk in a given pregnant woman is done by multiplying the risk associated with her age for the specific gestational age.

Currently, most prenatal tests consist of AFP, estriol and human chorionic gonadotropin (hCG), which is the triple test, which is a blood test that assesses the risk in a pregnancy of having a Down syndrome or spina bifida It is not a test that tells us whether or not the fetus has any of these defects. It is a test that tells us the probability of risk of having them. Studies have shown that about 70% of fetuses with Down syndrome can be identified early combining the analysis of the mother's age and the results of the triple test.

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.