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In medicine, the term abortion refers to the interruption of an early pregnancy due to any source, either spontaneous or deliberate. Spontaneous abortions, also known as miscarriages, occur in up to 15 percent of pregnancies. An inevitable abortion is a situation in which vaginal bleeding, abdominal pain, cramps, and cervical dilation occur in a pregnant woman and eventually lead to a miscarriage. Once the cervix dilates, it is unlikely that any medical intervention will prevent the loss of the pregnancy. The passage of large blood clots or tissue through the vagina also indicates an inevitable abortion.
Many factors contribute to an inevitable abortion. In the first trimester of pregnancy, 90 percent of miscarriages stem from genetic or chromosomal abnormalities. Maternal diseases, such as diabetes, hypertension, lupus, and infections also increase the probability of miscarriage. Use of tobacco, alcohol, or other illicit drugs can hinder fetal growth and development, leading to a spontaneous loss of the pregnancy. Finally, anatomic abnormalities in the mother’s uterus, hormonal problems, and immunologic factors may account for more than 50 percent of miscarriages in the second trimester.
Evaluation for an inevitable abortion includes a pelvic examination during which the doctor observes the cervix to assess the extent of dilation and thinning that has taken place. An abdominal or vaginal ultrasound can determine whether the baby's development is appropriate for his estimated age and whether he still has a heart beat. Additionally, the physician will perform several blood tests, such as a complete blood count, a human chorionic gonadotropin (HCG) level, and a white blood cell count to evaluate the amount of blood loss or infection present and whether the pregnancy is still viable. A severe drop in the HCG levels indicates that the body has stopped producing this hormone that is essential for maintenance of a pregnancy.
Once an inevitable abortion progresses to a complete miscarriage, the expelled material can be examined to verify that the entire placenta has passed out of the mother's body. If part of the fetus or placenta remains inside the uterus, the mother has an increased risk for excessive bleeding or infection. A vacuum aspiration of the uterine contents, also called a dilation and curettage (D&C), may be essential to prevent these complications. In addition, the chromosomal makeup of the fetal tissue may be analyzed to determine whether a genetic defect caused the miscarriage.