question: Q:An 18-year-old primigravid woman comes for her initial prenatal visit at 16 weeks' gestation. She is not sure about the date of her last menstrual period but says that the pregnancy probably occurred immediately after she stopped taking oral contraceptives 5 months ago. Maternal serum α-fetoprotein (MSAFP) concentration is increased to 3 multiples of the median. Which of the following is the most appropriate next step in management?? 
  A:Repeat measurement of MSAFP concentration;B:Triple screening for MSAFP, serum β-hCG, and serum estriol concentrations;C:Ultrasonography;D:Amniocentesis for measurement of α-fetoprotein concentration