Can research subject to Subpart B and that includes pregnant women as subjects be exempt from the regulations, per $45$ CFR $46,$ if all of the conditions of the exemption are met?

No$,$ research with pregnant women can never be exempt per $45$ CFR $46\mathrm{.}104.$

Yes, if there are limits on the blood draw amounts included in the research.

Yes, each of the exemptions in $45$ CFR $46\mathrm{.}104$ may be applied to research subject to Subpart B$.$

Yes, but only for certain exempt categories per $45$ CFR $46\mathrm{.}104.$