Placenta Previa Normal Measurements

Placenta Previa Prior to 26 weeks: Normal ≥ 2cm : report as not low-lying, do not state a measurement. low-lying if placenta < 2cm from internal os, report as low-lying with the measurement and recommend rescan at 34 weeks After 26: If ≥ 5cm from internal os: report as clear of the cervix If < 5cm: state distance from internal os in cm’s Avoid using grading systems to describe relationship of the placenta to the internal os, rather the shortest distance between the lower margin of the placenta and the internal os should be reported. The term placenta previa should be reserved for use in the third trimester only. Common reasons for incorrect measurements include an overfull bladder, Braxton-Hicks contractions and placenta obscured by fetal parts. Consider scanning with the bladder empty, translabial scanning and transvaginal scanning to better delineate the cervix and placental margin

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