The Disadvantages of Prenatal Testing

If you're pregnant, prenatal testing may seem like a positive thing, a way to check your baby's health and find out whether you're having a boy or girl. While 97 percent of all prenatal tests deliver good news, according to the University of Tennessee Medical Center; prenatal testing can also reveal problems that force parents-to-be to make difficult choices about the pregnancy.

Finding Abnormalities

Most pregnant couples walk into their first prenatal ultrasound more excited than apprehensive about what the ultrasound may show. The first ultrasound functions as a screening test for major abnormalities; some of the potential problems that can be diagnosed are limb abnormalities, facial deformities or neural tube defects. Additional testing is usually needed to confirm or further diagnose a problem. Parents-to-be should be aware of the possibility of the discovery of something wrong while taking comfort in the fact that most pregnancies proceed without any problem

False Positives and Negatives

Pregnant woman getting ultrasound from doctor

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No testing is infallible. The triple screen, a test that assesses the risk of certain chromosomal disorders such as Down syndrome, does not diagnose a problem but assesses the risk that a baby has a chromosomal problem. The triple screen has around a 5 percent potentially positive rate, but most of these babies do not actually have genetic disorders, the Centre for Genetics Education states. Prenatal testing may not find every problem, especially if you don't do chromosomal testing but just have an ultrasound done. Even if you have chromosomal testing done, in rare cases maternal chromosomes instead of fetal chromosomes may be removed and tested.

Possible Pregnancy Loss

Although the risk is small, certain prenatal testing procedures such as amniocentesis or chorionic villus sampling may increase the risk of pregnancy loss. During CVS, your doctor withdraws a small amount of tissue from the placenta to test the chromosomes. The chance of pregnancy loss after CVS is less than 1 percent, according to the Center for Genetics Education. During amniocentesis, your doctor inserts a thin needle into the abdomen and withdraws a small amount of fluid to test the chromosomes within the fluid. The miscarriage rate following amniocentesis is less than one in 200, according to the University of Tennessee Medical Center.

Fetal Damage

Pregnant woman getting ultrasound from doctor

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Although rare, invasive procedures such as CVS or amniocentesis can also cause fetal damage. Chorionic villus sampling done early in pregnancy, before 63 days of gestation, can in rare cases cause limb shortening in the fetus. A University of Milan study published in the October 1992 issue of "Prenatal Diagnosis" reported a limb reduction risk of 1.6 percent with CVS performed very early in pregnancy, between six to seven weeks.