Prenatal tests

Non-invasive prenatal testing, known by its acronym NIPT (Non-Invasive Prenatal Testing), analyzes small fragments of DNA from the pregnancy that circulate freely in the pregnant person's blood. Because it only requires a maternal blood draw, it carries no risk of pregnancy loss, unlike invasive procedures.

At Aclimu we offer two versions. Basic NIPT assesses the risk of the most common trisomies (21, 18, and 13) and of sex chromosome abnormalities. Expanded NIPT adds the analysis of microdeletions and other chromosomes. In both cases, it is a screening test: it estimates a risk; it does not confirm a diagnosis. Sensitivity for trisomy 21 is very high (>99%); for sex chromosome aneuploidies (Turner, Klinefelter) and microdeletions, sensitivity and positive predictive value are lower, and a positive result always requires diagnostic confirmation.

NIPT is mainly designed to estimate the risk of trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome), which are among the most common chromosomal abnormalities. Expanded NIPT also assesses microdeletions and additional chromosomes. It is important to know what it does NOT do: it does not replace ultrasounds or obstetric checkups, and it does not detect every possible congenital condition.

Analysis of fetal DNA in the mother's blood is generally done starting at week 9 to 10 of pregnancy, once there is enough DNA from the pregnancy circulating in the blood. The medical society ACOG recommends offering cell-free DNA screening to all pregnant people, regardless of age or prior risk level. The exact timing should always be decided with your regular healthcare provider.

This is important to understand clearly: NIPT is a screening test, not a diagnostic test. According to the American College of Obstetricians and Gynecologists (ACOG), cell-free DNA testing is the most sensitive screening test for the most common aneuploidies, but it is not the same as a diagnostic test. It can produce false-positive and false-negative results.

This means that a high-risk result does not, on its own, confirm that the baby has a chromosomal abnormality, and a low-risk result does not completely rule one out. If you get a high-risk result, international recommendations advise talking with your medical team and considering a confirmatory diagnostic test, such as chorionic villus sampling or amniocentesis, ideally with genetic counseling.

Fetal sex determination identifies the baby's sex by looking for Y-chromosome sequences in the fetal DNA present in the mother's blood. It is usually done starting at week 9 of pregnancy, when the technique's reliability is high, with a simple blood draw and no prescription needed.

Separately, first-trimester biochemical screening combines markers in the mother's blood (the free fraction of β-hCG [human chorionic gonadotropin] and the protein PAPP-A) with maternal age and ultrasound data such as nuchal translucency. According to a study carried out at a public maternity hospital in Argentina, this combined screening is performed between weeks 11 and 13.6 and makes it possible to estimate whether the risk of aneuploidy is increased or decreased; it is a screening method, not a diagnosis.