Chapter 15: Prenatal Diagnostic Tests

Ultrasonography serves as a foundational imaging modality, with transvaginal approaches during the first trimester and transabdominal imaging in later pregnancy enabling assessment of gestational age, fetal viability, and anatomical development. Doppler ultrasound analysis evaluates blood flow patterns in the umbilical artery to determine placental adequacy and detect vascular compromise. Serum screening protocols, including Maternal Serum Alpha-Fetoprotein and multiple-marker panels, identify pregnancies at elevated risk for neural tube defects such as anencephaly and spina bifida alongside chromosomal abnormalities including trisomy 21. Invasive diagnostic procedures offer definitive genetic diagnosis through Chorionic Villus Sampling during the first trimester or Amniocentesis in the second trimester for karyotyping and assessment of fetal lung maturity via the lecithin-to-sphingomyelin ratio and phosphatidylglycerol presence. Percutaneous Umbilical Blood Sampling provides direct fetal blood access for managing hemolytic disease and Rh sensitization complications. Antepartum surveillance methods form a critical component of fetal assessment, with the Nonstress Test evaluating fetal heart rate acceleration patterns and autonomic nervous system function, often incorporating vibroacoustic stimulation to minimize false reassuring results. The Contraction Stress Test identifies placental insufficiency by analyzing fetal heart rate responses to induced uterine contractions. The Biophysical Profile integrates multiple assessment parameters including fetal breathing movements, gross body movements, muscle tone, heart rate reactivity, and amniotic fluid volume measurement through the Amniotic Fluid Index to evaluate both acute and chronic hypoxia markers and detect oligohydramnios. Throughout these diagnostic and surveillance procedures, nursing care focuses on patient education, emotional support, and facilitating informed decision-making as families navigate the psychological and ethical complexities of prenatal testing.