Dating ultrasound for amnio
As the age of a mother increases, the chance of her having a baby with a chromosomal abnormality also increases.The most common chromosome abnormality is Down Syndrome.This is a test which may be offered to a woman whose age, family or medical history, nuchal or blood test results suggest that she may have a higher than normal risk of having a baby with a chromosomal or genetic abnormality.Together you, your partner and your doctor can decide whether it is appropriate for you to have this test.Some factors to consider include: Down syndrome screening results You had a screening test that indicated your baby is at a higher-than-average risk for Down syndrome or another chromosomal problem.Ultrasound results An ultrasound showed that your baby has structural defects associated with a chromosomal problem.
While an amniocentesis can be performed at any stage in pregnancy, it is usually done at around 15 weeks.Between 35 and 40 years of age, the chance of having a baby with a chromosomal abnormality is approximately 1 in 150.Beyond the age of 40 years this chance increases even further.(In about 1 percent of cases, there's a problem with the specimen and the test doesn't yield a result.)Amniocentesis is usually done when a woman is between 16 and 20 weeks pregnant.Though all women should be offered the option of having an amnio, women who choose to have this test are often those at increased risk for genetic and chromosomal problems, in part because the test is invasive and carries a small risk of miscarriage.