PRENATAL AND PRE-IMPLANTATION
Article provided by Super Religare Laboratories
GENETIC DIAGNOSIS
couples can opt for prenatal diagnosis. In recent years there is the availability of preimplantation genetic diagnosis (PGD). Prenatal diagnosis or prenatal screening
is caused by numerical chromosome imbalance or aneuploidy. There is
A evidence that 50% of the first trimester
spontaneous abortions are aneuploid. Chromosomal errors are known to be common in early human embryos and probably make a significant contribution to early pregnancy loss and implantation failure in IVF patients. Couples with genetic disorders including recessive or dominant single gene defects, sex linked conditions, or chromosomal rearrangements face a reproductive risk: affected pregnancies may result in birth of a child with significant phenotypic abnormality, sometimes resulting in early neonatal death. Such
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significant proportion of pregnancy wastage
is testing for diseases or conditions in a foetus or embryo before it is born. There are a variety of non-invasive and invasive techniques available for prenatal diagnosis. Each of them can be applied only during specific time periods (gestational age) during the pregnancy for greatest utility. The techniques employed for prenatal diagnosis include non-invasive procedures like ultrasonography, foetal blood cells in maternal blood, maternal serum alpha- fetoprotein, maternal serum beta-HCG, maternal serum estriol. Invasive procedures include Chorionic villus sampling during 8-12 weeks of gestation, Amniocentesis during the second trimester at preferably 16-18 weeks. The third trimester cord blood sampling is also performed in certain cases where the pregnancy has not been monitored throughout and there is a late identification of intra uterine growth retardation wherein the diagnosis will confirm or rule out common syndromes in the foetus.
In some patients it is useful to diagnose high-risk pregnancies early so that delivery can be scheduled in a tertiary care hospital where the baby can receive appropriate care. The aim is to detect birth defects
such as neural tube defects, Downs syndrome, chromosome abnormalities, genetic diseases and other conditions such as spina bifida, cleft palate, Tay-Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis and Fragile X syndrome. Screening can also be used for prenatal sex discernment to detect X linked disorders. ACOG (American College of Obstetricians and Gynecologists) guidelines currently recommend that all pregnant women, regardless of age, be offered
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