Placenta accreta spectrum refers to abnormal placental attachment to the myometrium. Which history increases risk?

• A. Prior cesarean delivery and placenta previa.
• B. Maternal smoking.
• C. Multiparity with no prior cesarean.
• D. First pregnancy.

Answer: (A)

Abnormal placentation in the placenta accreta spectrum is most strongly linked to uterine scarring, which most often comes from prior uterine surgery. The combination of a prior cesarean delivery and placenta previa creates a scarred area where the decidual layer is deficient, allowing placental villi to attach to and invade the myometrium more deeply. This is why the history of a prior cesarean delivery with placenta previa is the strongest risk factor for placenta accreta spectrum.

Other factors like maternal smoking, multiparity without a prior cesarean, or a first pregnancy do not carry the same strong association with abnormal placental attachment.