Pregnancy loss refers to death of the fetus at any time during pregnancy. Pregnancy loss most commonly occurs during the first trimester, when it is referred to as early pregnancy loss. Placenta praevia or vasa praevia refers to the placenta or fetal blood vessels, respectively, covering or being located close to the opening of the uterus. More than half of patients affected by placenta praevia (51.6)% have bleeding before delivery. Vasa praevia occurs in about 0.6 per 1000 pregnancies. Placental abruption involves the separation of the placental lining from the uterus of the mother. It occurs most commonly around 25 weeks of pregnancy. Uterine rupture is when the muscular wall of the uterus tears during childbirth or, less commonly, during pregnancy. Nontubal ectopic pregnancy refers to an ectopic pregnancy that occurs in the ovary, cervix, or intra-abdominal cavity.Other causes of early pregnancy bleeding include the following:

Postcoital bleeding, which is vaginal bleeding after sexual intercourse that can be normal with pregnancy. Iatrogenic causes, or bleeding due to medical treatment or intervention, such as sex steroids, anticoagulants, or intrauterine contraceptive devices. Vaginal or cervical bleeding, which may arise from many causes including fibroids, polyps, warts, tumors, vaginitis, or trauma. Importantly, these causes may co-occur with other causes of early pregnancy bleeding. Lower genitourinary tract bleeding, which may result from a urinary tract infection (UTI), strenuous exercise, or bladder cancer. Pathophysiology
Early pregnancy bleeding is usually from a parental source rather than a fetal one.
The parental source may be a disruption in the vessels of the decidua or a lesion in the cervix or vagina. In the earlier stages of pregnancy, the cervix can be vulnerable to bleeding as new blood vessels are being grown. Vasa praevia is a rare condition that can result in bleeding from the fetoplacental circulation. Vasa praevia happens most often when the umbilical cord grows in a way that it directly enters the membrane, and therefore blood vessels that are unprotected by the umbilical cord or placental tissue can rupture and lead to bleeding. Another common source of bleeding can be due to abnormal development of the embryo. The most common early fetal abnormality is abnormal number of chromosomes causing loss of the pregnancy and bleeding. Diagnostic approach
The initial assessment of vaginal bleeding in early pregnancy must first consider hemodynamic stability and the degree of pain or bleeding. A hemodynamically unstable patient would necessitate an immediate transfer to the emergency department . It is important to recognize that patients may suffer significant blood loss before any signs of hemodynamic instability are evident.The initial evaluation of early pregnancy bleeding involves a history and physical examination. The relevant history includes determining the gestational age of fetus and characterizing the bleeding. Bleeding that is at least as heavy as menstrual bleeding or associated with clots, tissue, lightheadedness, or pelvic discomfort is associated with increased risks of ectopic pregnancy and spontaneous abortion.