and women older than 35 are at increasing risk as they get older. Women who have had previous pregnancies (multiparity), especially a large number of closely spaced pregnancies, are at higher risk due to uterine damage. Smoking during pregnancy; cocaine use during pregnancy Women with a large placentae from twins or erythroblastosis are at higher risk. Race is a controversial risk factor, with some studies finding that people from Asia and Africa are at higher risk and others finding no difference. Placental pathology (velamentous insertion, succenturiate lobes, bipartite i.e. bilobed placenta etc.) Baby is in an unusual position: breech (buttocks first) or transverse (lying horizontally across the womb). Placenta previa is itself a risk factor of placenta accreta. Alcohol use during pregnancy was previously listed as a risk factor, but is discredited by this article. Classification Traditionally, four grades of placenta previa were used, but it is now more common to simply differentiate between "major" and "minor cases. Other than that placenta previa can be also classified as: Complete: When the placenta completely covers the cervix Partial: When the placenta partially covers the cervix Marginal: When the placenta ends near the edge of the cervix, about 2 cm from the internal cervical os Diagnosis History may reveal antepartum hemorrhage. Abdominal examination usually finds the uterus non-tender, soft and relaxed. Leopold's maneuvers may find the fetus in an oblique or breech position or lying transverse as a result of the abnormal position of the placenta. Malpresentation is found in about 35% cases. Vaginal examination is avoided in known cases of placenta previa. Confirmatory Previa can be confirmed with an ultrasound. Transvaginal ultrasound has superior accuracy as compared to transabdominal one, thus allowing measurement of distance between placenta and cervical os. This has rendered traditional classification of placenta previa obsolete. False positives may be due to following reasons: Overfilled bladder compressing lower uterine segment Myometrial contraction simulating placental tissue in abnormally low location Early pregnancy low position, which in third trimester may be entirely normal due to differential growth of the uterus. In such cases, repeat scanning is done after an interval of 15–30 minutes. In parts of the world where ultrasound is unavailable, it is not uncommon to confirm the diagnosis with an examination in the surgical theatre. The proper timing of an examination in theatre is important. If the woman is not bleeding severely she can be managed non-operatively until