What Causes Trace Of Ketone And Blood In Urine During Pregnancy?

Hi I am 13 and a half weeks pregnant and have a trace of ketone and blood in urine aren't in pain scanned regularly as 3rd baby had rhesus disease of newborn and severe anaemia so are closely being monitored by fetal medicine but been told ketone is dehydration and to drink more and wonder where blood trace has come from
Thank you
Please reassure me