During Preconception Counseling the Nurse Tells a Woman That the Most

During preconception counseling the nurse tells a woman that the most critical time in the development of a baby is between conception and week eight.What is the nurse's most important rationale for this statement?

A) To emphasize the need to avoid teratogenic substance while trying to get pregnant
B) To emphasize the need to do frequent pregnancy tests while trying to conceive
C) To explain why many pregnancies are spontaneously aborted in the first trimester
D) To explain the need to avoid ultrasound examinations in the first trimester