Fetus or newborn affected by placenta praevia

**Definition:** Placenta praevia exists when the placenta lies wholly or in part in the lower segment of the uterus. Diagnosis has evolved from the clinical I-IV grading system, and is determined by ultrasonic imaging techniques relating the leading edge of the placenta to the cervical os. Grade I is a low lying placenta, Grade II is a placenta that meets the edge of the cervical os, Grade III is a placenta that partially covers the os, and Grade IV is a placenta that completely covers the os.