Which diagnostic study is most informative for evaluating fetal anatomy and placental function in a gestation around 29 weeks?

• A. Amniocentesis
• B. Ultrasonography
• C. Chorionic villus sampling
• D. Maternal serum alpha-fetoprotein

Answer: (B)

Ultrasonography is the most informative tool at around 29 weeks because it noninvasively provides real-time visualization of fetal anatomy and placental structure, along with measurements of fetal growth. It can assess organ development, detect anatomical anomalies, determine placental location and maturity, and evaluate placental function through Doppler flow studies of the umbilical artery and other fetal vessels. In contrast, invasive tests like amniocentesis or chorionic villus sampling are used for genetic or chromosomal information and carry risks, making them inappropriate for routine anatomy assessment at this stage. Maternal serum alpha-fetoprotein is a screening test for open fetal defects earlier in pregnancy and does not give detailed anatomical or placental functional information. Therefore, ultrasound (with Doppler as needed) provides the most comprehensive view of both fetal anatomy and placental function at this gestational age.