I just read an article on placenta previa. This is a condition where the pacenta is in position in the uterus lower down than the baby and thus in in position to come out first during delivery. This condition is a leading cause of death from pregnancy, but it can be discovered by sonogram and medically managed. The primary risk is massive hemorrhage and preterm delivery. Might be a good idea in later preganancy to ask the doctor if the placenta appears to be in the right position, so a potential problem won’t simply be missed.
A baseline CBC count with a platelet count is useful. Prothrombin time, activated partial thromboplastin time, fibrinogen, and fibrin split products may also be helpful because retroplacental bleeding has been associated with consumptive coagulopathy.
The most useful and least expensive imaging study is ultrasonography. Transabdominal ultrasonography has 95% accuracy. Transvaginal ultrasonography provides 100% accuracy in identifying placenta previa. An important caveat is the phenomenon termed placental migration. This occurs when placenta previa is identified early in pregnancy and resolves as the pregnancy proceeds. For example, ultrasonograms performed early in the second trimester identify placenta previa in 5-15% of patients, with 90% of these resolving by term. Similarly, 26% of the total cases of placenta previa and only 2.5% of the cases of partial or marginal placenta previa diagnosed in the second trimester persist into the third trimester. This does not represent true migration of the implantation site but, rather, differential growth of the placenta and distention of the myometrial cavity away from the os.
Other tests include: fetal monitoring, Rh testing (patients who are Rh negative and unsensitized and who present with painless vaginal bleeding require Rh-immune globulin), and a Kleihauer- Betke test to detect excessive fetomaternal hemorrhage (>30 mL) that would necessitate additional Rh-immune globulin therapy.