What is Prenatal Testing?
Prenatal testing is performed on an expectant mother prior to delivery to ascertain any probable disabilities or disease. These tests aid identification of defects at birth such as chromosome abnormalities and genetic diseases, 
Down Syndrome, neural tube defects, and other conditions like such as spina bifida, cleft palate, tay sachs disease, fragile x syndrome, thalassemia, cystic fibrosis, and sickle cell anemia. Procedures for testing include sonograms, amniocentesis, genetic screening or serum marker testing and nuchal translucency ultrasound. They also help determine fetal sex, probability of fetal abortion, mother’s health and risky pregnancies, so that correct measures may be taken for the baby and the mother to be cared for appropriately.
Prenatal tests are conducted to identify conditions that may be classified as ‘mild’, ‘severe’ or affecting life expectancy. They enable would-be parents to take corrective action for treatable conditions or make special arrangements for lifelong impairment. These tests also facilitate making the decision of terminating a pregnancy in case of a foreseen disability.
Conducting prenatal diagnosis is mainly to serve three purposes:
- to offer timely medical or surgical help for a condition before or after birth,
- to allow parents the choice of aborting a fetus with a hopeless condition, and
- to give parents the opportunity to “prepare” themselves for the psychological, social, financial, and medical problems related to a baby with a health condition or the probability of a stillbirth.
Being informed before the birth would allow health care staff and parents to prepare themselves better for the delivery of a child with a health problem. For example cardiac defects are often with linked with Down Syndrome and may need immediate intervention upon birth.
Many expectant parents are interested in sex determination prior to baby’s birth and use methods like prenatal ultrasound and amniocentesis with karyotyping.
Methods of diagnostic testing could be invasive or non-invasive.
Amniocentesis is an invasive test conducted by inserting needles and probes into the placenta and is done within 14 to 20 weeks gestation period. Chorionic villus sampling is done within 9.5 to 12.5 weeks of gestation. Both these procedures offer a slight risk to the fetus.
Non-invasive methods or ‘screening’ are only used to evaluate risk of disease but do not determine a fetal condition conclusively.
Examples of non-invasive techniques are genetic tests done for Down Syndrome, Trisomy 13, and Trisomy 18 to show up abnormality in genes or chromosomes. An in-depth ultrasound can provide a definitive diagnosis in case of neural tube defects non-invasively.
Prenatal testing may not necessarily be conducted to establish birth defects. Other reasons like female-infanticide, designer-babies for parents who are looking to have parent-specific traits in their offspring have raised some legal and bioethical issues.
Prenatal tests mostly offer useful information. In rare cases, they could lead to miscarriages or have undesirable effects on mothers and babies. The related medical expense and anxiety are avoidable.
The decision of undergoing these tests is of course, entirely up to the parents who may think it necessary to do so for their own peace of mind.