question: Q:A 29-year-old woman, gravida 2, para 1, at 17 weeks' gestation comes to the physician for a routine prenatal examination. A prenatal ultrasound at 10 weeks' gestation showed no abnormalities. Serum studies at 16 weeks' gestation showed an abnormally elevated α-fetoprotein level and normal beta human chorionic gonadotropin and estriol levels. After genetic counseling, the patient decides to continue with the pregnancy without any diagnostic testing. The remainder of her pregnancy is uncomplicated and she delivers a boy at 38 weeks' gestation. Analysis of the infant's leukocytes shows a 46, XY karyotype. Which of the following is the most likely cause for the abnormal second-trimester test results?? 
  {'A': 'Robertsonian translocation', 'B': 'Underestimation of gestational age', 'C': 'Spina bifida occulta', 'D': 'Maternal hypothyroidism', 'E': 'Gestational trophoblastic disease'},