ABSTRACT
An abnormally invasive placenta (AIP) is one of the most serious complications of pregnancy being associated with massive post-partum bleeding, high maternal morbidity and mortality, and a high frequency of post-partum hysterectomies. Risk factors can increase the likelihood of AIP but are not required for the diagnosis. These include advanced maternal age, assisted conception, and smoking. The associations of these risk factors are weak and do not form a good basis for a screening test. AIP is directly linked to previous Caesarean sections—in particular elective procedures where the scar is likely to be placed in the lower uterine segment rather than the cervical canal as with most emergency Caesarean sections in labor. Any woman with a previous Caesarean section and a placenta praevia in this pregnancy should be assessed for an AIP in the early third trimester. The most reliable ultrasonographic markers of AIP are increased placental thickness and placental lacunae.
