Prenatal diagnosis of any abnormalities can be done by a range of available prenatal tests.
These prenatal tests can detect birth defects such as neural tube defects, Down 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.
Some tests and checks during gestation are routine, such as Ultrasounds.
However more invasive methods such as amniocentesis for detecting birth defects are done only when indicated.
In the usual course, only non invasive techniques and tests are considered; such as the examination of the woman’s uterus from outside the body, obstetric ultrasounds from 7 weeks to confirm pregnancy dates, the specialized nuchal scan when you are 11 weeks to 13 weeks pregnant may be used to identify higher risks of Down’s syndrome.
Later morphology scans when you are 18 weeks pregnant may check for any abnormal development. External fetal monitoring may be done when indicated.
The obstetrician will also routinely check the fetal heartbeat; check the pregnant woman’s blood pressure, weight and other physical characteristics.
More invasive methods of detecting fetal abnormalities may be considered:
- If a woman has become pregnant for the first time when over the age of 35
- If a woman has previously had one or more miscarriages, premature babies or babies with a birth defect, especially heart or genetic problems
- If a woman has previously had a still birth or the child has died soon after birth
- If a woman has high blood pressure, lupus, diabetes, asthma, or epilepsy
- If the pregnant woman has a family history or ethnic background prone to genetic disorders, or whose partners have these
- Women who are pregnant with multiples (twins or more)
In the event that the above factors raise the possibility of complications and birth defects, then invasive methods of testing are considered, such as Chorionic villus sampling, Amniocentesis Embroscopy and fetoscopy. These methods are however associated with the chance of a miscarriage (with Chorionic villus sampling there is chance about 1% and with Amniocentesis it is about .5%). So the probable risks have to be considered prior to getting any invasive tests done.
Even after the tests are conducted and results indicate some or other abnormality, women have to consider whether they are emotionally and physically prepared to abort the fetus, because it is the very few cases wherein any kind of corrective measures can be carried out on the fetus.