19 weeks pregnant, my 13 weeks scan shows have simple ovarian cyst - size of 30mm. but my dr didn't say anything about it. should that be concerned?

No: Most early ovarian cyst found on ultrasound are physiologic cyst. Most likely a corpus luteum cyst. Hormones secreted by the corpus luteum maintains the pregnancy early in pregnancy. This cyst usually resolve. However if the cyst bleeds, ruptures or there is a tortion( twisting ) of the pedicle, this may cause pain. If concerned ultrasound my be repeated in 6 weeks. Don't worry, be happy.