Prenatal testing is a term that describes many tests that are done during pregnancy. The tests provide information about your health and the health of your developing baby. Prenatal testing includes blood and urine tests and ultrasounds. In some cases, more invasive procedures may be recommended. Invasive tests may include sampling placental tissue, drawing fluid from the amniotic sac, or drawing fetal blood from the umbilical cord.

Prenatal tests can be used to identify many different things, including:

    
  • Treatable health problems in the mother that can affect the health of the fetus
  • Characteristics of the fetus, including size, age, placement in the uterus, and sex
  • Genetic, or chromosomal problems
  • In the mother, prenatal tests are used to identify things that could possibly affect the developing fetus, including:

        
  • Antibodies that can cross the placenta and affect the health of the fetus
  • Gestational diabetes
  • Immunity to certain diseases (such as chickenpox and German measles)
  • Iron-deficiency anemia
  • Sexually transmitted diseases
  • Prenatal tests can screen for many different congenital defects in the fetus, including:

        
  • Chromosomal disorders: such as Down syndrome (trisomy 21), trisomy 18, and trisomy 13. The risk of having of child with a chromosomal disorder increases with the age of the parents.
  • Dominant gene disorders: such as Huntington disease and achondroplasia
  • Recessive gene disorders: such as cystic fibrosis, sickle cell disease, Tay-Sachs disease, and beta thalassemia
  • Neural tube defects: such as spina bifida and anencephaly
  • Congenital heart defects
  • About 250 different birth defects can be diagnosed through prenatal testing. Some can be treated in utero (before birth) or immediately after birth, but the majority cannot. Prenatal testing can be quite complicated. However, prenatal tests do not test for everything, and no prenatal test guarantees the birth of a healthy baby.