What is the Difference Between NIPT and Amniocentesis?

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Noninvasive Prenatal Testing (NIPT) and amniocentesis are two different techniques used to screen for or diagnose chromosomal abnormalities in a fetus. Here are the main differences between the two methods:

NIPT:

  • Noninvasive: NIPT requires only a small blood draw from the pregnant person, posing no physical risks to the pregnant person or fetus.
  • Screening test: NIPT is a genetic screening, not a diagnostic test, and can only indicate whether there is a chance a condition exists.
  • Can be done as early as 9 weeks of pregnancy.
  • Primarily looks for signs of Down syndrome, Edwards syndrome, Patau syndrome, and conditions caused by missing or extra X and Y chromosomes.
  • Can also determine the expected sex of the baby.

Amniocentesis:

  • Invasive: Amniocentesis is an invasive prenatal test that carries a slight risk of miscarriage (0.1%).
  • Diagnostic test: Amniocentesis is a diagnostic test that can detect chromosome abnormalities and other genetic conditions that may not be detectable by NIPT.
  • Typically performed during the second trimester of pregnancy.
  • Can detect a wider range of genetic conditions compared to NIPT.

In summary, NIPT is a noninvasive screening test that can be performed earlier in pregnancy and has no physical risks, while amniocentesis is an invasive diagnostic test that can detect a wider range of genetic conditions but carries a slight risk of miscarriage. The choice between the two tests depends on the individual's preferences and medical history.

Comparative Table: NIPT vs Amniocentesis

Here is a table comparing Non-Invasive Prenatal Testing (NIPT) and Amniocentesis:

Feature NIPT Amniocentesis
Method Uses the baby's DNA in the placenta and maternal blood Uses the amniotic fluid surrounding the fetus
Invasiveness Non-invasive Invasive
Timing Can be performed anytime after 9 weeks into the pregnancy Performed when a woman is between 15 to 20 weeks in gestation
Sensitivity >=99.96% for trisomy 21, trisomy 13, and trisomy 18 Not available
Specificity >=99.96% for trisomy 21, trisomy 13, and trisomy 18 Not available
Positive Predictive Value 91.67% for trisomy 21, 66.67% for trisomy 13, and 100% for trisomy 18 Not available
Primary Purpose Detects chromosomal abnormalities, such as Down syndrome, trisomy 18, and trisomy 13 Detects genetic and chromosomal abnormalities
Secondary Purpose Cannot be used for prenatal sex discernment, unlike amniocentesis Can be used for prenatal sex discernment
Miscarriage Risk No risk, as it is non-invasive Carries a small risk of miscarriage due to the invasive nature of the procedure

NIPT is a non-invasive prenatal diagnostic technique that uses cell-free fetal DNA found in the maternal blood to detect certain chromosomal abnormalities, such as trisomy 21, trisomy 18, and trisomy 13. Amniocentesis, on the other hand, is an invasive prenatal diagnostic technique that involves extracting a small amount of amniotic fluid containing fetal tissues from the amniotic sac and examining the fetal DNA for genetic abnormalities. While NIPT can be performed anytime after 9 weeks into the pregnancy, amniocentesis is usually performed between 15 to 20 weeks in gestation.