29 yr old multiparous lady with history of LSCS suggests low lying placenta on USG at 20 weeks gestation. MRI clearly delineates irregular large placenta with villi invading myometrium with subtle bleed on T1 and FFE with villi not reaching to serosa and beyond suggesting invasive placenta of increta variety

















Teaching points by Dr MGK Murthy and Mr Samuel MRI technician





1.Low lying placenta is placental edge that comes within 2 cm of cervix on USG (better measured on TVS). Invasive placenta are (a) Accreta , abnormally adherent placental villi attached directly in to myometrium, but not invade it (b) Increta is villi invade myometrium when they reach serosal surface , percreta is suggested





2. Placenta previa (normally 1 in 300 patients ) is higher with advancing age , history of Caesarean, with maternal mortality (3 per 1000 cases)and abruption placenta possible





3. Invasive placental aetiologies include impairment of the apparent relative cranial migration (with differential growth rates of uterus)/ scarred lower uterine segment not growing adequately in 3rd trimester, smoking (hypoxic mechanism), thin, incompletely developed or absent decidua basalis (including protective nitabuchs layer), multiparous lady (because of thicker palcenate), any circumstance leading to damaged uterus or myometrium or decidua etc





4. Overdistended bladder may produce false previa on USG(routine use of post void scan in high risk useful). TVS is specific to low lying placenta in view of proximity. Transperineal USG may help





5. USG shows absence of normal retroplacental clear space, placental tissue contiguous with myometrium, prominent venous lakes, vascularity (abnormal basal plate) , absent hypoechoic zone suggesting decidua defect. Doppler shows continuum of lacunar flow from placenta through myometrium





6.Treatment of invasive variety is obviously challenging including bleeding, thrombolysis, thromboprophylaxis after delivery etc and is usually individualized



