What would be the most common cause of her clinical scenario?

Abruptio placentae -patient presentation women with an acute abruption classically present with the abrupt onset of vaginal bleeding, mild to moderate abdominal and/or back pain, and uterine contractions. back pain is prominent when the placenta is on the posterior wall of the uterus. the uterus is often firm, and may be rigid and tender. contractions are usually high frequency and low amplitude, but a contraction pattern typical of labor is also possible and labor may proceed rapidly. vaginal bleeding ranges from mild and clinically insignificant to severe and life-threatening. blood loss may be underestimated because bleeding may be retained behind the placenta and thus difficult to quantify. the amount of vaginal bleeding correlates poorly with the degree of placental separation and does not serve as a useful marker of impending fetal or maternal risk. maternal hypotension and fetal heart rate (fhr) abnormalities, however, suggest clinically significant separation that could result in fetal death and severe maternal morbidity. when placental separation exceeds 50 percent, acute disseminated intravascular coagulation and fetal death are common. in 10 to 20 percent of placental abruptions, patients present with only preterm labor, and no or scant vaginal bleeding. in these cases, termed concealed abruption, all or most of the blood is trapped between the fetal membranes and decidua, rather than escaping through the cervix and vagina. therefore, in pregnant women with abdominal pain and uterine contractions, even a small amount of vaginal bleeding should prompt close maternal and fetal evaluation for placental abruption. in other cases, a small concealed abruption may be asymptomatic and only recognized as an incidental finding on an ultrasound. occasionally, the signs and symptoms of abruption develop after rapid uterine decompression, such as after uncontrolled rupture of membranes in the setting of polyhydramnios or after delivery of a first twin. signs and symptoms of abruption also may occur after maternal abdominal trauma or a motor vehicle crash. in these cases, placental abruption generally presents within 24 hours of the precipitating event and tends to be severe. the clinical presentation and obstetrical evaluation of pregnant trauma victims are described in detail separately. (see trauma in pregnancy, section on evaluation and management.) laboratory findings the degree of maternal hemorrhage correlates with the degree of hematological abnormality; fibrinogen levels have the best correlation with severity of bleeding. initial fibrinogen values of 200 mg/dl are reported to have 100 percent positive predictive value for severe postpartum hemorrhage, while levels of 400 mg/dl have a negative predictive value of 79 percent. mild separation/hemorrhage may not be associated with any abnormalities of commonly used tests of hemostasis. severe abruption can lead to disseminated intravascular coagulation (dic). dic occurs in 10 to 20 percent of severe abruptions with death of the fetus.