Limited diagnostic prenatal ultrasounds provide basic data about the baby and your pregnancy including fetal heartbeat, number of gestations, placental location, fetal position, and fetal gender. Limited diagnostic ultrasounds should be viewed as an addendum to, not a substitution for, the Level 1 Screening Ultrasound typically performed before week 12, or the Level 2 Fetal Anatomical Survey typically performed between the 18th and 22nd weeks of pregnancy.