Prenatal screening: Nursing

Prenatal screening can be done to identify the likelihood that a certain fetal disorder or condition is present. Screening is typically completed during the first and second trimesters and can be followed by diagnostic testing to confirm if the fetus is affected.

Alright, so first trimester screenings are done between 11 to 14 weeks of gestation to look for evidence of chromosomal abnormalities, including aneuploidies, which means there’s an abnormal number of chromosomes. These tests include nuchal translucency, or NT, using ultrasound; as well as a measurement of maternal serum levels of pregnancy-associated plasma protein-A, or PAPP-A; human chorionic gonadotropin, or hCG; and cell-free fetal DNA, or cfDNA.

Nuchal translucency measures the fluid-filled space behind the fetus' neck. An increased amount of fluid is associated with chromosomal abnormalities, including Trisomy 21, also known as Down syndrome, where there’s an extra copy of chromosome 21.

Next, PAPP-A is a glycoprotein made by the placenta. Low levels of PAPP-A are also linked to Trisomy 21. Then, there’s hCG, which is a hormone made by the placenta. Increased levels of hCG are associated with Trisomy 21, whereas decreased levels are associated with both Trisomy 18, or Edward syndrome, where there’s an extra copy of chromosome 18; and Trisomy 13, known as Patau syndrome, where there’s an extra copy of chromosome 13.

Lastly, cfDNA refers to fragments of DNA from the breakdown of maternal and fetal cells. cfDNA can be used to screen for trisomies, sex chromosome aneuploidies, and other chromosomal microdeletions or duplications.