Exposed to roseola at 31 weeks pregnant. what could this do to my unborn child if i get it?

Roseola: There is no evidence that exposure to Roseola in pregnancy has any negative effect on the mother or fetus. See the following PDF link for Information. http://www.ucsfchildcarehealth.org/pdfs/illnesses/Roseola_0509.pdf

Roseola in pregnancy: Evidence suggests that 95% of pregnant women are already immune to Roseola as a result of previous exposure as a child, and active disease in a pregnant woman is rare. In the event of new exposure in early pregnancy, increased risk of miscarriage is present. Active disease later in pregnancy increases risk of birth defects. Your obstetrician would likely want to be made aware of this exposure.

Nobody knows: more than 80 to 95% of the population in the US have been exposed during infancy with the HHV - 6 virus that causes Roseola - so the likelihood is high that any given pregnant woman already has anti-bodies and is protected. in terms of viral diseases obstetricians are typically concerned about rubella, chickenpox, HIV, parvovirus B 19, and CMV, not so much HHV - 6.