Is it possible for fifth disease to be transferred to a woman's fetus in the 3rd trimester?

Yes: If the mom has her primary experience with this virus at any point in pregnancy, the fetus can become infected. If it happens, the most disabling effect seems to be it's effect on the babies blood forming activity. If it slows it down or stops even briefly, the fetus may not be able to keep up with the metabolic demands of growth & a condition called hydrops can result.