When discussing CHD risk with a patient at 8 weeks gestation, which development timeline is accurate?

• A. Depends on causative factors
• B. We don't really know
• C. First trimester
• D. Third to fifth weeks

Answer: (D)

Cardiac development happens during a very brief early window in pregnancy, and most congenital heart defects arise from events that occur during that time. The heart forms, loops, and undergoes septation and outflow tract development mainly in weeks three to five of gestation. By eight weeks, the basic cardiac structures are already in place, so the accurate timeline to discuss CHD risk is the third to fifth weeks. The broader label of the first trimester is less precise, and statements implying we don’t know or that causative factors dominate the timing don’t fit the established pattern of heart morphogenesis. Emphasize to the patient that the critical period for CHD development is during weeks three to five of gestation.