Which Causative Factor Would Change Exposure to the Zika Virus

Which causative factor would change exposure to the Zika virus from a direct to an indirect association with microcephaly?

A) The pregnant female travels to an area where the virus is prevalent.
B) All exposed pregnant females were positive for the virus and anemic.
C) The fetuses exposed during the first trimester experienced microcephaly.
D) Fetuses not treated for the virus before birth exhibited microcephaly.