A 20-year-old G2P1 patient comes to see you at 17 weeks gestational age to review the results of her triple test done 1 week ago. You tell the patient that her maternal serum a-fetoprotein (MSAFP) level is 2.0 multiples of the median (MOM). The patient's obstetrical history consists of a term vaginal delivery 2 years ago without complications. What do you tell your patient regarding how to proceed next?