A 24-year-old primigravida at 14 weeks of gestation presents for a routine first-trimester anomaly scan following an elevated maternal serum alpha-fetoprotein (5.2 MoM). She has been on sodium valproate for epilepsy since before conception with no periconceptional folic acid supplementation. Transabdominal ultrasound reveals a live fetus with the findings marked as **A** in the diagram—absence of the cranial vault and cerebral hemispheres above the orbits, with prominent "frog-eye" appearance and an exposed, disorganized, vascularized neural remnant overlying the skull base. Polyhydramnios is noted (AFI 26 cm). Which of the following is the most appropriate next step in counseling and management?