What is a first trimester screening for a fetus?

Blood and U/S tests.: First trimester screen for any pregnancy includes a sonographic examination to determine plurality, basic fetal anatomy, gestational sac location, fetal viability and gestational dates - as well as blood tests (hcg, papp-a, maternit21/harmony tests) to determine the risk for down syndrome, fetal growth restriction, preeclampsia (uterine artery dopplers), preterm birth (cervical length). Nicolaides.