A postpartum client is to receive the Rubella vaccine prior to discharge from the hospital. Why is she instructed to not become pregnant for 4 weeks after receiving this vaccine?

The vaccine is a live virus and may cause birth defects in the fetus.

Tests to determine if the client developed immunity are not accurate for a month.

She may have the virus and feel too sick to tolerate a pregnancy.

Her body is not ready to nurture another pregnancy so quickly.