A 39-Year-Old Primigravida Thinks That She Is About 8 Weeks

A 39-year-old primigravida thinks that she is about 8 weeks pregnant, although she has had irregular menstrual periods all her life. She has a history of smoking approximately one pack of cigarettes a day, but she tells you that she is trying to cut down. Her laboratory data are within normal limits. What diagnostic technique could be used with this pregnant woman at this time?

A) Ultrasound examination
B) Maternal serum alpha-fetoprotein screening (MSAFP)
C) Amniocentesis
D) Nonstress test (NST)